In recent years, the public dimensions of Habsburg-Ottoman diplomacy have drawn increasing scholarly attention. This interest stems not only from the rich documentary record that survives but also from historiographical developments that have emphasized the symbolic and performative aspects of early modern political culture and diplomacy.Footnote 1 Recent scholars have explored topics such as ceremonial practice, symbolic language, ritual, propaganda, and the representation of rule. Particular focus has been placed on the arrivals and departures of diplomatic missions in Vienna and Constantinople—events closely observed by local populations and used by diplomats to represent their sovereigns, themselves, and key ideas about inter-imperial relations.Footnote 2 The dissemination of news of these events was further facilitated through broadsheets, official reports, newspapers, and images made before, during, or after the missions. Audiences with the emperor in Vienna and the sultan in Constantinople—carefully staged before select publics—as well as the ritual exchange of gifts, have likewise received considerable scholarly attention.Footnote 3 This is particularly evident in studies of the grand embassies, one of the most distinctive features of Habsburg-Ottoman diplomacy. Primarily aimed at conflict resolution and the maintenance of peace, these diplomatic missions were often theatrical in nature and staged before audiences.Footnote 4 Even some peace treaties between the Habsburgs and the Ottomans found their way into print, rendering them partially accessible to a wider reading public.Footnote 5
This article, however, shifts focus from these visible aspects to the hidden dimension of diplomacy: its secrecy. The historiography of secrecy in early modern diplomacy has attracted increased attention from researchers in recent years but remains fragmentary, largely because covert practices, by their very nature, generated fewer sources. Nonetheless, recent studies—especially those influenced by the methodological innovations of the so-called new diplomatic history—have begun to illuminate themes such as espionage, information gathering, the circulation of knowledge, postal infrastructures, intelligence networks, and the mediality of diplomatic communication, as these constitute characteristic features of early modern diplomacy.Footnote 6 Yet, the role of secrecy itself remains only selectively explored or only touched on briefly in research on Habsburg-Ottoman diplomacy.Footnote 7 Indeed, early modern diplomats operated not only in public view but also in secret, often deliberately excluding broader audiences from critical aspects of their work.Footnote 8 Espionage, coded messages, strategic deception, concealment, and the manipulation of information were all integral practices in their professional repertoire.
This article first interrogates the diplomats’ understanding of secrecy. Second, it maps the fields of diplomatic practice where this concept was paramount, and third, it analyzes the practical application of secrecy in these fields. Taken together, these findings suggest that secrecy was a core component of Habsburg diplomacy at the Sublime Porte. The focus of this study is the seventeenth and early eighteenth centuries, a period particularly suited to this investigation. During these centuries, diplomatic ties between the Habsburg monarchy and the Ottoman Empire had become institutionalized, creating a growing need at the imperial court in Vienna for reliable and timely information concerning Ottoman affairs. As a result, a significant and sustained transfer of knowledge occurred via Habsburg diplomats stationed in Constantinople. Moreover, the diplomatic activities of this period are well documented in surviving archival sources, allowing for an in-depth exploration of both the public and secret aspects of diplomacy. Although the study incorporates the sixteenth century in some instances, existing scholarship provides few reference points for this period. Consequently, achieving a longitudinal perspective that situates these findings within broader historical developments would require extensive additional source work.
The analysis of the hidden dimension of diplomacy faces significant conceptual and methodological challenges, particularly the difficulty of clearly distinguishing between “official” and “unofficial” diplomacy. This is further complicated by the ambiguity of terms such as “secret service” or “secret diplomacy.”Footnote 9 Consequently, this study adopts the contemporary understanding of secrecy held by the imperial diplomats in Constantinople as its empirical starting point. This approach aligns with the actor-centered perspective, a dominant framework in current diplomatic history. The article is structured as follows: the first section outlines the central features of Habsburg-Ottoman diplomacy in the early modern period, whereas the second examines contemporary Habsburg diplomats’ conceptualizations of secrecy, establishing the methodological point of departure of the analysis. The third section focuses on the secret dimensions of the communicative practices of Habsburg envoys in Constantinople, examining how secrecy was enacted, communicated, and functionally embedded in the envoys’ interactions with the Ottoman and imperial courts.
Habsburg-Ottoman Diplomacy in the Early Modern Period
Diplomatic relations between the Habsburg monarchy and the Ottoman Empire represent a long-standing and multifaceted historical phenomenon, originating in the late fifteenth century.Footnote 10 These contacts ended in 1918 with the dissolution of both Austria-Hungary and the Ottoman Empire at the close of World War I. Habsburg-Ottoman diplomacy developed under conditions of significant structural tension, shaped by the expansionist trajectories of both powers. The Habsburgs had emerged as a dominant dynastic force within the European political order at the turn of the late Middle Ages to the early modern period, while the Ottomans had successfully transformed their small principality in western Anatolia into a transcontinental empire within the span of two centuries. The antagonism between the two imperial entities was rooted in overlapping geopolitical ambitions, exclusive claims to universal rule, entrenched cultural oppositions, mutual perceptions of enmity, and profound religious divisions. Between 1526 and 1792, these hostilities culminated in eight distinct military conflicts, collectively referred to in the Holy Roman Empire as the Türkenkriege (“Turkish Wars”), a term that entered contemporary usage and was employed by figures such as Martin Luther.Footnote 11 Until approximately 1600, the Ottoman military maintained clear superiority in land warfare, though their naval strength was comparatively weaker. From the early seventeenth century onward, the strategic balance began to shift, especially following the failed Ottoman siege of Vienna in 1683, which marked a turning point. By the eighteenth century, the rivalry between the two empires had diminished in strategic importance, as other political priorities evolved for both powers.
Recent historiographical developments have increasingly challenged traditional binary interpretations of Habsburg-Ottoman relations. Scholars have drawn attention to shared and overlapping networks, sustained diplomatic and commercial channels, transcultural spaces, contact zones, and regional trade interactions.Footnote 12 The religious divide, while historically salient, is now frequently interpreted as a factor that was politically instrumental rather than inherently antagonistic.Footnote 13 This scholarly reevaluation is further supported by evidence of conflict management and peace-building efforts on both sides.Footnote 14 A growing body of literature has shifted focus to the intermediaries who operated between the two empires—individuals now variously described as “go-betweens,” “transimperial subjects,” or “cultural brokers.” These figures—including diplomats, dragomans (interpreters), merchants, missionaries, travelers, and pilgrims—played a key role in facilitating cross-cultural exchange and contributed to the permeability of what were long perceived as impermeable imperial boundaries.Footnote 15 While diplomacy primarily functioned as a bridge, it simultaneously possessed the potential to engender friction and expose underlying fault lines. On the one hand, Habsburg diplomats functioned as a unifying force, serving as pivotal agents in the transfer of knowledge and culture between Constantinople and Vienna. Conversely, they entrenched existing divisions by perpetuating enemy stereotypes and emphasizing the alterity of the Ottomans.Footnote 16 Therefore, a balanced (dis-)connected perspective, which incorporates both integrative and disjunctive phenomena, is essential for a more comprehensive analysis.Footnote 17
Until well into the eighteenth century, diplomacy remained the principal channel of contact between the two empires, as economic relations lagged behind those that the Ottomans maintained with other European powers, such as Venice, France, England, and the Netherlands.Footnote 18 By 1566, the Habsburgs had dispatched more than forty diplomatic missions to the Ottoman court in Constantinople and, beginning in 1547, maintained a permanent chargé d’affaires (resident) in the city. By contrast, the Ottoman Empire favored the use of temporary, ad hoc legations for specific ceremonial or diplomatic occasions, with approximately forty such missions recorded by 1748. The Habsburgs, too, occasionally employed temporary envoys, but the broader diplomatic relationship remained asymmetrical—a practice that was also evident in the Ottomans’ relations with other European powers. This imbalance began to recede only in 1797, with the establishment of a permanent Ottoman embassy in Vienna.Footnote 19
The underlying causes of this diplomatic asymmetry remain a subject of ongoing scholarly debate. It would be reductive to attribute it solely to a general Ottoman disinterest in the West. While the Ottomans may have exhibited relatively less proactive engagement than their European counterparts, this difference likely reflects a complex constellation comprising civilizational self-perception, religious identity, and strategic calculation. Comparable attitudes of cultural superiority were present in European polities as well, yet these did not prevent the establishment of permanent representatives in Constantinople.
Conceptualizations of Secrecy among Habsburg Diplomats
As Habsburg diplomats left no theoretical treatises offering systematic reflections on their conception of secrecy, the subject necessitates in-depth methodological consideration. In early modern political culture, conceptions of secrecy were widespread, as exemplified by the discourse on the arcana imperii (secrets of state). A notable articulation appears in the work of Traiano Boccalini (1556–1613), News from Parnassus (Ragguagli di Parnaso), first published in Venice in 1615. In this satirical work, Boccalini envisions a fantastical marketplace in which political tools are sold: brushes that paint white objects black, spectacles that render errors invisible, and optical instruments that distort perception—making elephants appear as mosquitoes and dwarfs as giants. There are also candies designed to mask the metaphorical “bad breath” caused by the prolonged concealment of secrets.Footnote 20
At this time, the idea that secrecy was a structural and necessary element of political governance—and that subjects were not entitled to full knowledge of state affairs—was already widely recognized in early modern Europe. Niccolò Machiavelli articulated this position most explicitly in his treatise The Prince (Il Principe, ca. 1513), in which he justified deception, dissimulation, and concealment as legitimate tools of sovereign rule. The rationale was straightforward: knowledge equates to power; informational asymmetry confers strategic advantage; ignorance invites vulnerability.Footnote 21 The concept of secrecy was so pervasive that it gave rise to a distinct literary genre—arcana literature—closely associated with raison d’état theory. Drawing on Tacitean categories, early modern theorists distinguished between the relatively accepted arcana imperii (secrets that preserved the state) and the more ethically contentious arcana dominationis (secrets that served merely to uphold the ruler’s power). While this discourse gradually declined after 1650, it persisted long into the eighteenth century. In sum, early modern political thought recognized secrecy not merely as an incidental feature of governance, but as a functional and, at times, necessary mode of rule.Footnote 22
Conceptions of secrecy are also discernible in early modern treatises on diplomatic theory. These works proliferated from the sixteenth century onward—especially following the institutionalization of permanent diplomatic missions—and many circulated widely via repeated editions and translations.Footnote 23 Two particularly influential texts illustrate this discourse. The first is The Ambassador and His Duties (L’Ambassadeur et ses fonctions) by Abraham de Wicquefort (1606–82), published in 1682.Footnote 24 This work, available in both German and English translations, remained a standard reference for diplomats into the nineteenth century. Wicquefort, a Dutch-born diplomat, served at several European courts, including that of Louis XIV. The second is On How to Negotiate with Sovereigns (De la manière de négocier avec les souverains), by the French diplomat and writer François de Callières (1645–1717), published in 1716.Footnote 25 Both treatises provide deep insight into how diplomacy was viewed in the seventeenth century and for a significant period became canonical in diplomatic theory and practice. They constitute two paradigmatic examples of a long tradition of reflection on secrecy in diplomacy.
Wiquefort and Callières explore the ideal attributes and professional conduct expected of envoys, with particular attention to secrecy. Callières emphasizes that a model diplomat must conceal his thoughts and intentions, never divulging his true objectives. A diplomat was expected to master the art of disguise to better extract sensitive information and to exercise emotional restraint, ensuring that secrets were not betrayed in moments of anger or frustration.Footnote 26 Strategic discernment was equally crucial; the envoy needed to distinguish which pieces of information warranted strict confidentiality and which could be shared in exchange for valuable intelligence.Footnote 27 Techniques such as lying, dissimulation, and concealment were thus considered not only permissible but professionally necessary. However, such practices posed ethical tensions.Footnote 28 While instrumental for diplomatic success, they risked damaging the moral integrity of the envoy and the reputation of the sovereign he represented. Diplomatic codes of conduct thus evolved to balance practical exigency with normative restraint.
Although it remains unclear whether Habsburg envoys at the Sublime Porte had direct exposure to the discourse on the arcana imperii and the treatises on the theory of diplomacy, their correspondence and practices suggest a tacit familiarity with these conceptualizations and codified norms. Diplomatic skill was often acquired through practice (learning by doing), and supplemented by precedent, archival study, and informal transmission via diplomatic networks. The missions of predecessors served as guidance and were regarded as precedents, in keeping with the contemporary view of history as historia magistra vitae (“history is the teacher of life”). Additionally, many rules and norms became widespread through circulation within diplomatic circles and networks. It is to be expected that the envoys were familiar with the main rules and norms of diplomatic theory because there are clear indications in the sources that everyday knowledge on how to be a good and successful diplomat existed. However, as this subject remains largely under-researched, it is premature to offer definitive assertions at this stage. It is also impossible to ascertain with certainty the extent to which these standards were already operative in Habsburg-Ottoman diplomacy in the sixteenth century. However, there are indications that antecedents existed.
A historical analysis of the terminology offers a more nuanced understanding of the diplomats’ conceptions of secrecy. The German terms geheim and Geheimnis were widely employed in early modern texts. These terms conveyed meanings such as “familiar,” “hidden,” and “concealed,” but also “enigmatic” and “intimate.” The sophisticated semantic range of “secret” is best exemplified by the term Geheimer Rat (Secret resp. Privy Council), one of the imperial court’s most pivotal governing bodies. In this context, geheim connoted both “trustworthy” and “confidential”—two nuances that were inextricably intertwined and thus impossible to clearly distinguish.Footnote 29 A semantic overlap exists with the term privat (“private”), which is occasionally used interchangeably and construed as the antonym of public. Yet, privat also carries additional connotations, denoting “without ties to the state” or “on one’s own behalf.”Footnote 30
The Latin secretus—an older term that entered English via French as secret—encompassed a semantic range including “clandestine,” “divided,” and “separated.” A secretarius, accordingly, was understood to be a trusted writer or confidant. In conceptual-historical terms, secretus also connoted seclusion and spatial or social remoteness. The Latin arcanum similarly played a prominent role, even frequently appearing in German-language sources.Footnote 31 These concepts were applied across a broad array of domains, including religion, philosophy, technology, medicine, alchemy, personal character traits, anatomical references, and—most relevant for this study—politics and diplomacy.
The diplomatic correspondence between Habsburg envoys at the Sublime Porte, and the imperial court in Vienna demonstrates the frequent and context-specific use of terms such as geheim, secret, and vertraut. In the letters, diplomats regularly reported their activities in Constantinople—an essential part of their responsibilities alongside negotiation, imperial representation, and information gathering. The successful execution of these duties was crucial not only for the fulfillment of the diplomatic mission but also for the accumulation of symbolic, material, and cultural capital necessary for socio-cultural distinction and career advancement within the imperial court. To meet these expectations, envoys maintained a consistent reporting schedule, generally submitting letters to the imperial court and its institutions (Hofkriegsrat, Geheimer Rat, Hofkammer) at approximately two-week intervals. These dispatches covered a broad range of topics, including direct responses to court instructions, unsolicited updates on regional or local developments, and information deemed potentially useful to imperial interests. Although surviving responses from Vienna are comparatively rare, they nonetheless illuminate the interactive and bidirectional character of early modern diplomatic communication. It is no overstatement to claim that diplomatic correspondence constitutes one of the most vital sources—if not the most vital—for the study of early modern international politics.Footnote 32
From a methodological perspective, the analysis of such correspondence must take into account its mediality—that is, the formal, rhetorical, discursive, and material conditions that governed its production, transmission, and reception. These letters were composed according to established conventions and communicative norms that structured both content and form, thereby shaping the handling and articulation of sensitive or confidential information. Influences included classical and contemporary theories of epistolography, the personal and institutional interests of the envoy, the nature of the diplomatic relationship between sender and recipient (emperor, imperial court), and the cumulative intertextuality of serial correspondence.Footnote 33 Theoretical writings on diplomacy also played a formative role in these conventions. Notably, François de Callières set forth stylistic guidelines that emphasized clarity, concision, and factual precision in diplomatic writing.Footnote 34
The correspondence of Alexander Greiffenklau von Vollrats (d. 1648), who served as Habsburg’s chargé d’affaires in Constantinople from 1643 to 1648, offers a compelling case study of secrecy as a structural principle in early modern diplomatic communication. His letters regularly employ secrecy-related terminology—geheim, vertraut, secret—across a variety of diplomatic contexts. In a letter dated June 1643, for example, Greiffenklau reported that a dragoman had disclosed in secret the grand vizier’s uncertainty regarding how to respond to a Habsburg request. In the same letter, Greiffenklau requested funds to support the covert transmission of sensitive dispatches.Footnote 35 In subsequent letters, the diplomat refers to confidential reports, secret conferences—for example, between Muscovite envoys and Ottoman officials—as well as interactions between Armenian emissaries and Safavid agents, with the parties described as being engaged in covert planning.Footnote 36 He also mentions the use of secret couriers, confidential informants, clandestine intelligence, and covert negotiations between Swedish and French envoys. In one notable instance, Greiffenklau recounts urging the Venetian envoy to notify the emperor in confidence of a potential Turkish military mobilization.Footnote 37 The motif of secret correspondence (geheime korrespondenz) recurs throughout the corpus, denoting a specialized infrastructure designed to ensure the secure transmission of sensitive information between the Habsburg mission in Constantinople and the imperial court. Greiffenklau also repeatedly refers to the need for financial resources to facilitate bribery—commonly framed as a means of uncovering a secret.Footnote 38 He uses the term privat to denote personal matters (such as a dispute between the grand vizier and another dignitary), as well as settings situated outside the formal public sphere (such as an audience in the garden rather than in the Divan chamber).Footnote 39 In summary, Greiffenklau’s letters reveal three principal fields of activity in which secrecy operated as a fundamental principle of diplomatic practice: negotiation and social interaction, information gathering, and reporting. Each of these fields will be analyzed in greater depth in the following section.
Secrecy was also integral to these three spheres of activity of Habsburg diplomats in Constantinople during the sixteenth century, a period in which the clandestine acquisition and transmission of intelligence to the imperial court constituted a core diplomatic function. Consequently, envoys routinely employed methods of concealment, bribery, espionage, and encryption.Footnote 40 These operational modalities involved a broader network of actors beyond the envoys themselves, encompassing secretaries, scribes, and translators. However, determining the specific degree of agency they exercised within these clandestine operations is often problematic. Furthermore, these activities represented a standard diplomatic modus operandi within the metropolis in general. As a key theater for early modern secret diplomacy, Constantinople fostered an environment where political and social interactions relied on both formal and informal mechanisms designed to secure intelligence and achieve mission objectives. Footnote 41
Secrecy in Diplomatic Practice
Negotiation and Social Interaction
One of the central tasks of early modern diplomats in Constantinople was to conduct negotiations and engage in dialogue with both Ottoman dignitaries and representatives of other powers. Consequently, diplomats relied on written instructions to navigate their mission, and these instructions delineated the boundaries of discretion for negotiations and interpersonal exchanges. For instance, in 1719, Emperor Charles VI explicitly instructed Count Damian Hugo von Virmont—who was sent as grand ambassador to the Sublime Porte—to keep all trade negotiations strictly confidential.Footnote 42 Representatives of other powers were to be informed only after an agreement had been finalized. When the full content of diplomatic instructions needed to remain confidential, a separate secret instruction (geheime instruktion) was issued. In some cases, these were to be opened only under certain circumstances. Count Herman Czernin (1576–1651), who served as grand ambassador to the Sublime Porte from 1644 to 1645, received such a sealed letter containing further concessions to be used if negotiations stalled. He ultimately returned the letter unopened because it was not needed.Footnote 43
It was a common diplomatic practice in the early modern period to conclude secret treaties or to attach confidential clauses to otherwise public agreements.Footnote 44 For example, during the lead-up to the War of the Spanish Succession, France and the Habsburg monarchy secretly agreed on the division of the Spanish Empire without notifying the other European powers.Footnote 45 However, such secret agreements appear to have played a minor role in Habsburg-Ottoman relations during this period. Nonetheless, secrecy was vital in day-to-day diplomatic interactions. This applied, first and foremost, to conversations between Habsburg diplomats and both Ottoman officials and foreign envoys. These talks aimed to uncover the secrets (arcana) of others while revealing none of their own, adhering closely to the normative expectations of early modern diplomacy, in which disclosing one’s secrets was considered taboo. A typical example is Alexander Greiffenklau’s conversations with various Ottoman dignitaries and diplomats from other powers, in which he attempted to discover the outcomes of meetings between envoys of George I Rákóczi, Prince of Transylvania (r. 1630–48), and Queen Christina of Sweden (r. 1632–54). These negotiations, held in Constantinople, were connected to a potential anti-Habsburg alliance.Footnote 46
Habsburg diplomats also closely monitored other foreign envoys’ negotiations with the Ottomans. Their reports reveal a keen awareness of whether these talks were being conducted in secret and whether their content had been made public. When secrecy was suspected, the diplomats often speculated about the possibility of covert agreements or alliances. For instance, in 1644, Greiffenklau viewed the secret negotiations between the French ambassador and representatives of the Sultan with suspicion, fearing the formation of a hostile alliance.Footnote 47 Another feature of negotiations was dissimulation—that is, the strategic concealment or denial of one’s true intentions. Diplomats deliberately masked their genuine views of the Ottomans during discussions. Overall, the tension between public and secret information was evident in the interactions of Habsburg envoys with both Ottoman officials and representatives of other powers.
Information Gathering
Another principal task of early modern diplomats was the systematic gathering of information about the host, particularly its closely guarded state secrets.Footnote 48 This objective was one of the key motivations behind the development of permanent diplomatic missions, a practice that originated in fifteenth-century Italy. By the end of the sixteenth century, much of Europe was already interconnected through a dense network of permanent legations. Constantinople was especially fertile ground for this, serving as a key hub for the exchange of information between Europe and Asia. News from many regions around the world passed through the city.Footnote 49 However, the boundary between information gathering and outright espionage was fluid, an ambiguity that was acknowledged in early modern diplomatic theory.Footnote 50 François de Callières, for instance, emphasized that although collecting intelligence was among a diplomat’s most important official responsibilities, it had to be conducted with the utmost discretion to avoid damaging the reputation of one’s sovereign. In other words, information gathering was to be undertaken covertly.Footnote 51
According to reports from Habsburg diplomats, considerable time and effort were invested in these activities. The diplomats’ primary goal was to uncover the arcana of the Ottoman Empire and those of other powers represented in Constantinople. Yet, reconstructing their precise methods is difficult, as the sources often provide only fragmentary details. For example, in 1632, Johann Rudolf Schmid zum Schwarzenhorn, who served as chargé d’affaires at the Sublime Porte from 1629 to 1643, requested several hundred ducats to pay his informants for intelligence that, he claimed, could potentially save “billions.”Footnote 52 As was customary, he did not name his sources, since espionage was punishable by death. In most cases, informants were referenced obliquely in reports as secret correspondents (geheime korrespondenten) or trusted persons (vertraute personen).Footnote 53 Sometimes, no specific person was named at all; the information was simply described as confidential.Footnote 54 However, in certain letters, diplomats did identify their sources by name—particularly when the reliability of the information needed to be demonstrated. The emperor and his court expected verified facts, not unfounded speculation, and thus, the correspondence occasionally includes subtle clues about the individuals who provided the information. Although no evidence has been found of envoys artificially classifying information as secret, whether to boost its currency or to project a larger web of sources, this behavior remains a plausible conjecture.Footnote 55
The information networks established by Habsburg diplomats in Constantinople were vital to this endeavor. The networks consisted of a broad range of contacts: Ottoman officials, secretaries, merchants, missionaries, travelers, soldiers, and Jews.Footnote 56 Particularly valuable were the envoys of other foreign powers, with whom Habsburg representatives regularly exchanged information. As per the saying, “one hand washes the other,” obtaining information in this context often required giving something in return. The challenge, therefore, lay in securing intelligence while revealing nothing of value. Accordingly, diplomatic reports frequently emphasized that information had been acquired without compromising secrets.Footnote 57
The density and structure of these networks varied depending on several factors. Political relations between states certainly played a significant role because envoys from hostile powers typically maintained greater distance from one another than did envoys from friendly powers. However, political rivalry did not entirely preclude the exchange of information; personal rapport could sometimes transcend official antagonism. There are documented instances of diplomats from opposing states who developed cordial relations and exchanged intelligence on a regular basis. For example, despite the ongoing rivalry between the Habsburgs and the French, their representatives in Constantinople remained in periodic contact. Diplomatic reports often assessed which foreign envoys could be considered trustworthy sources and which should be regarded with skepticism.
Ottoman dignitaries also frequently appeared as sources of information. These included viziers, grand viziers, the Sheikh-ul-Islam, members of the military, and even the sultan’s mother, who, as valide sultan, wielded enormous political influence. Dragomans were also well informed, though their motivations were not always transparent. While they were positioned to know a great deal, eliciting reliable intelligence from them could be difficult because they frequently pursued their own interests. However, widespread corruption did provide certain advantages to foreign diplomats: secret information was often obtainable through gifts and bribes. Yet, many Habsburg envoys complained of a chronic lack of funds—an enduring theme in their correspondence. This may have been exaggerated for strategic purposes, either to secure additional resources or to underscore the diplomat’s effectiveness despite fiscal constraints, thereby bolstering his standing at court.Footnote 58 However, upon his unexpected death in Istanbul, Greiffenklau left behind substantial debts.
Although the total extent of these costs cannot be established with absolute certainty, research based on available records from 1580 to 1583 suggests that the resident dedicated just under 20 percent of total expenditures to intelligence tasks such as espionage and communication. The frequency of these transactions is telling: nearly 40 percent of all accounting entries concerned the acquisition of intelligence, confirming that this function was already central to the quotidian duties of the envoys.Footnote 59
Spies also played a central role in the broader information apparatus. Reflecting a convention established in the sixteenth century, the identities of these actors were systematically masked to mitigate the risk of identification in the event of the unauthorized seizure of letters.Footnote 60 Nevertheless, the circle of individuals engaged in espionage was large and diverse. It included servants, secretaries, merchants, missionaries, soldiers, and others. According to current research, the majority were men, though recent scholarship has suggested that women and particularly maids were more involved than previously assumed. Some spies were employed for short-term assignments, others served for years.Footnote 61 Their methods ranged from simple observation to the interception of correspondence, including breaking seals and copying letters. The threat of double agents and counterespionage was ever-present. Consequently, as discussed, trustworthiness was a central criterion for evaluating informants and is frequently emphasized in diplomatic reports.
The Ottomans, by contrast, operated their intelligence networks differently. They did not maintain permanent diplomatic missions in Europe until the very end of the early modern period. To compensate for this absence, they developed an espionage system of their own. Though little research has been conducted on its internal mechanisms, recent studies suggest that it functioned effectively, at least in the Mediterranean region.Footnote 62
Reporting
Habsburg diplomats were expected to not only gather information but also record it and dispatch their findings to the emperor or imperial court. Throughout their missions, they produced regular reports and, in many cases, submitted a final report (final relation) upon returning to Vienna, summarizing their experiences and observations. Occasionally, this final account was supplemented by a separate secret report (geheim bericht). For example, after serving as internuncio (highest diplomatic rank after grand ambassador) in Constantinople for Emperor Leopold I in 1649, Johann Rudolf Schmid zum Schwarzenhorn submitted a secret report containing detailed insights into conditions within the Ottoman Empire and a critical analysis of its political system.Footnote 63
Letters were by far the most important medium of reporting. Through regular correspondence, Habsburg diplomats kept the emperor informed of significant developments in Constantinople.Footnote 64 The following discussion explores the role of secrecy in this correspondence, focusing on three core aspects: content, the use of ciphers, and the transport of the letters to Vienna.
Content: Determining the veracity of these reports is complex. Despite a formal requirement for neutrality and truthfulness, individual reporting was likely compromised by self-interest. To justify the hardships of the mission, envoys needed to satisfy their superiors in Vienna. It is difficult to determine precisely what diplomats chose to omit from their letters, yet this is an important endeavor to understand their use of secrecy. As such, one must infer what was not written. It is reasonable to assume that envoys carefully selected the information they conveyed and deliberately concealed certain details. Camouflage, deception, and concealment were tactics employed both in negotiations with the Ottomans and in reporting back to the imperial court, as diplomats operated under significant pressure to succeed. Diplomatic service entailed high personal costs and was intended to enhance symbolic, cultural, social, and material capital, often serving as a stepping stone for career advancement. Conversely, failure could jeopardize these aspirations. As a result, diplomats’ letters rarely contained references to personal emotions; emotional restraint was a key behavioral norm in early modern diplomacy.Footnote 65 In contrast, their Ottoman interlocutors were often portrayed as emotionally volatile. One vivid example comes from a 1633 report by Schmid zum Schwarzenhorn, recounting a ceremonial dispute with a high-ranking Ottoman official. The official, allegedly losing his composure, shouted, “You giauro [an Islamic slur for non-believers]! Will you no longer show me respect? I will strike you down like a dog!” The letter then describes him storming out and refers to him as “the roaring wild ox.”Footnote 66 Schmid zum Schwarzenhorn, on the other hand, kept his composure. Robyn Dora Radway’s analysis of albums created at the Deutschem Haus (German House) in Constantinople, which served as the residence for envoys and their retinues until the mid-seventeenth century, demonstrates that emotions were not absent from the diplomatic historical record. These albums document a range of sentiments, including homesickness, joy, a sense of community, love, and fear. However, this is only one case in point. The articulation of emotions and emotionality in the dispatches of Habsburg diplomats in Constantinople has yet to be systematically examined.Footnote 67
Diplomatic norms also demanded that the individuality of envoys be effaced in official reporting. They were expected to remain objective and background themselves in their narratives. However, a close reading of their letters reveals traces of personal identity and ego construction. Case studies, currently limited to the seventeenth century, suggest that diplomats frequently styled themselves as devout Christians and loyal subjects, dedicated to upholding imperial honor and rendering unwavering service. This constructed self—rooted in group identity and collective Christian values—masked personal interests. The diplomats thus projected an image of ideal service: loyal, dependable, and wholly devoted to the emperor and the House of Austria.Footnote 68
Secret codes: A distinctive feature of early modern diplomatic correspondence was the use of ciphers. François de Callières even devoted an entire chapter to this topic in his treatise on diplomacy. The decision to encrypt a letter depended on the sensitivity of its contents and the security of its delivery. When transport security was robust, encryption was often deemed unnecessary. For instance, Johann Jakob Kurz von Senftenau, who led a mission to the Sublime Porte from 1623 to 1624, chose not to encrypt a letter containing sensitive information because he had the opportunity to send it by secure means.Footnote 69 Entire letters could be encrypted, but sometimes, it was only individual paragraphs, sentences, or terms. Sensitive political information and passages in which the envoy reported on the sultan or his family were often encrypted, as were personal or geographical names.Footnote 70 This practice is similarly observable among Habsburg diplomats stationed in Constantinople during the sixteenth century.Footnote 71
Several cipher keys used by Habsburg diplomats in Constantinople have survived. Where keys are missing, they can often be reconstructed from marginal or interlinear decryptions written by imperial secretaries upon the letters’ arrival in Vienna. A good example of the encryption process can be found in the correspondence of Count Hermann Czernin, who traveled to Constantinople in 1644 as Ferdinand III’s grand ambassador. A seasoned diplomat, Czernin came from a distinguished Bohemian noble family and had previously traveled to Constantinople in 1616. He had also undertaken a pilgrimage to Jerusalem at the end of the sixteenth century and proven his loyalty to the Habsburgs through military service during the Thirty Years’ War. During his 1644–45 mission, he sent several letters to the emperor, many of which were encoded.Footnote 72
The cipher that Czernin used was a type of homophonic substitution known as a nomenclator, in which numbers replace individual letters, letter combinations, or names. This system was standard for Habsburg diplomatic practices at the time.Footnote 73 For example, “10” represented “a,” “11” stood for “b,” and so forth. To complicate decryption, multiple numbers could correspond to the same letter, for example, “57” and “63” also stood for “a,” while “56” could mean “b.” Some numbers represented letter combinations, such as “1” for “ac” or “2” for “ec.” Key terms were also encoded: “Asia” appeared as “179,” “Europe” as “207,” and “sultan” as “227.” The system was deliberately simple, striking a balance between security and practicality. Since both encryption and decryption were time-consuming and error-prone, the cipher needed to be manageable. For this reason, the same cipher was often used for a period of years. Although these texts were not impervious to decryption, they generally served their purpose. In the eighteenth century, cipher systems became more complex, reflecting a heightened concern with the secrecy of diplomatic correspondence.Footnote 74
Methods of transport: Information not only had to be gathered and recorded but also needed to reach Vienna safely. Count Hermann Czernin described such letters as “secret notes” (geheime handtbrieffel).Footnote 75 Furthermore, some letters were highly confidential and required special handling. The most secure method was to send the letters using a dedicated courier. However, this was costly and not always feasible, especially when no courier was available.Footnote 76 As a result, Ottoman couriers were frequently used to transport letters to the frontier, where Habsburg couriers took over. This method was relatively inexpensive, but the risk of interception by the Ottomans could never be ruled out entirely. Delays also occurred when Ottoman officials failed to forward the letters promptly.Footnote 77 Another option was to entrust letters to travelers such as merchants, although this method was also insecure and often slow, particularly if the route was indirect. For instance, some letters reached Vienna via Warsaw and took months to arrive. A more reliable alternative was the Venetian postal system, which generally functioned well thanks to the Italian Republic’s highly organized diplomatic apparatus. Yet even here, secrecy was not guaranteed. It was repeatedly discovered that letters had been opened en route, and the Venetian representative in Constantinople (bailó) occasionally refused to carry Habsburg correspondence.Footnote 78
So, how were letters containing highly sensitive material delivered? In some cases, special inks such as those made from lemon juice were used to conceal messages. In other cases, letters were smuggled out of the country, for example, hidden in bottles. Because such methods were cumbersome, a separate postal network known as the secret correspondence (geheime correspondenz) was established as early as the sixteenth century. This clandestine system consisted of a chain of stations, or bases, at which trusted agents (usually Christians or converts) received the letters and passed them along to the next stop until they reached the border, where Habsburg couriers took over.Footnote 79 These correspondents operated under formal contracts and expected compensation for their services. Diplomats were responsible for covering the cost, which, if they were fortunate, could be reimbursed by the imperial court as correspondence money (correspondenz geld).Footnote 80 Maintaining this network was time-consuming and fraught with challenges. Sources frequently report disruptions, because correspondents had moved, died, or were no longer performing their duties diligently. Replacing them was difficult because many feared being discovered by Ottoman authorities, and the remuneration was often considered insufficient.Footnote 81
Summary
While substantial scholarly attention has been devoted to the public dimensions of Habsburg-Ottoman diplomacy, its secret aspects—often obscured by a scarcity of sources—have long remained underexplored. By investigating the communicative strategies of imperial envoys in Constantinople, this article analyzes the spheres of activity regulated by secrecy. It explores how the imperative of concealment conditioned diplomatic agency and argues that secrecy served as a central organizing principle of Habsburg foreign policy. The initial analytical step involves a critical examination of the concept of secrecy. The widely disseminated contemporary discourse on arcana imperii, alongside treatises on diplomatic theory in which secrecy is a central theme, offers initial insights. While definitive evidence of the envoys’ direct engagement with these treatises remains elusive, they likely acquired a tacit familiarity with these norms through professional socialization—be it during the preparatory phase of their missions or via interaction within diplomatic networks. A more empirical substantiation is provided by a historical-semantic analysis of the terminology of secrecy employed in the envoys’ dispatches to the imperial court. The results highlight three principal fields of operation in which secrecy played a defining role in the communicative practice of Habsburg diplomats: negotiation and social interaction, information gathering, and reporting.
In their dealings with both Ottoman dignitaries and other foreign diplomats, Habsburg envoys aimed to uncover state secrets while disclosing as little as possible of their own. Diplomatic encounters were evaluated according to the level of secrecy they required or allowed and gathering information demanded substantial effort. To these ends, diplomats built extensive networks that relied on Ottoman officials, foreign representatives, and informants. Espionage and bribery, though costly, were central methods of acquiring sensitive information. The act of reporting was no less governed by secrecy. The envoys’ letters were shaped by both formal conventions, duties, and personal strategies. They often omitted inconvenient details or framed events to highlight their own effectiveness. Failures were typically attributed to external factors or the supposed unpredictability of the Ottomans, while overt expressions of emotion were avoided in keeping with diplomatic norms of restraint and self-control. To ensure the confidentiality of their reports, envoys used cipher systems that included homophonic substitution with nomenclators. The transport of correspondence to Vienna required particular care. In response, the court developed a dedicated courier system known as “secret correspondence,” operated by agents under contract. While intended to ensure secure delivery, this system required constant maintenance and funding because correspondents might relocate, die, or neglect their duties.
In conclusion, secrecy was a defining characteristic of Habsburg diplomacy in Constantinople. It permeated core activities—negotiation, information gathering, and reporting—and revealed the inherent tension between the public face of diplomacy and its covert operations. The intrinsic linkage between secrecy and diplomatic practice in this context offers a valuable analytical lens for understanding the institutional norms and strategic modalities that shaped Habsburg-Ottoman diplomatic relations.
The concealed aspects of Habsburg diplomats’ activities in the Ottoman capital remain a largely underexplored field of inquiry. Further systematic research is required across all domains in which secrecy played a constitutive role, including the acquisition and transfer of information, the employment of cryptographic methods, the conduct of negotiations, and the rhetorical deployment of secrecy in diplomatic correspondence. These elements must ultimately be analyzed in relation to one another to yield a more integrated understanding. In parallel, the dialectical relationship between public-facing and clandestine diplomatic practices warrants closer examination, given that Habsburg envoys operated continuously at the intersection of these two spheres. Moreover, the tension between normative diplomatic theory and the lived reality of communicative practice remains a critical area for further analysis. Future investigations should also contextualize these findings within a longue durée perspective, extending the analysis to the sixteenth and eighteenth centuries. Scholarship on the German House—the residence of Habsburg envoys and their retinues until the mid-seventeenth century—has identified secrecy as a central socio-political practice within its walls.Footnote 82 However, due to the paucity of existing research, it cannot yet be determined whether the conceptualization of secrecy there diverged from that of the imperial diplomats analyzed in the present study. Seemingly, distinct differences existed regarding the visual communication of confidential information within late sixteenth-century albums, which represent a specific source typology with a mediality distinct from that of epistolary correspondence.Footnote 83 Finally, the significance of secrecy in Ottoman diplomatic practice merits further scholarly investigation.
