In the eighth book of Lucan's Bellum Ciuile, Pompey sends the Galatian king Deiotarus into the distant East to seek an alliance with Parthia, the vast empire beyond the Euphrates ruled by the Arsacid dynasty.Footnote ¹ His instructions to Deiotarus begin with these lines (8.211–14):

Deiotarus must appeal to the Arsacid king personally, as Pompey goes on to explain; the ambassador's mission is ‘to bring my words to the proud Arsacid’, who rules Parthia.Footnote ² In his inclusion of the Arsacids among the drinkers of the Tigris and the Euphrates, however, Pompey misspeaks: as many Greco-Roman sources attest, the kings of ancient Persia drank exclusively from the Choaspes, a river in Susiana.Footnote ³ The misstatement is more than an errant remark, for it underlines the erosion of Pompey's erstwhile status as master of the East while highlighting the limits of Roman power over the Arsacid realm that Pompey professes to understand. This paper explains the error and connects it to recent discussions of the poem's shifting political geography in its later books.Footnote ⁴

The Choaspes tradition in Greco-Roman literature began in classical Greece during the reign of the Achaemenids in Persia. Herodotus mentions the river in his narrative of Cyrus’ career, though the report is framed as a general ethnographic observation about Persian royalty. The Great King, the author says, campaigns well stocked with provisions, ‘and, in particular, water is also brought from the Choaspes river, which flows by Susa, and from which river alone and none other the king drinks’.Footnote ⁵ According to Athenaeus, the same observation was found in the Persica of Herodotus’ contemporary Ctesias, who further explains that the river's water had a light and pleasant taste.Footnote ⁶ Related traditions are preserved in the fragmentary histories of Agathocles of Cyzicus and Dinon of Colophon. The former mentions a ‘golden water’ in Persia that only the king and his eldest son could drink, while the latter records an Achaemenid royal norm against the consumption of foreign food and drink that apparently began under Xerxes.Footnote ⁷

Neither the origin nor the veracity of these reports is significant for the present purposes; what matters is that the Choaspes tradition found its way into Greek and Latin literature in the Roman empire, whose inhabitants viewed the Parthian kingdom of their day as the successor to Achaemenid Persia.Footnote ⁸ Thus Tibullus refers to the ‘royal water’ of the Choaspes without specifying whether the royalty involved are Achaemenids or Arsacids.Footnote ⁹ But in a Roman context this was in some ways an artificial distinction, especially in Latin verse. In one of the Odes, for example, Horace conflates the two dynasties and speaks of the contemporary Arsacid king Phraates IV ‘restored to the throne of Cyrus’.Footnote ¹⁰ The identification of Parthia as Persia's successor was common in literature from the Late Republic onward, and in poetry not least.Footnote ¹¹ In the Roman imagination the Arsacids inherited not only the territories of the Achaemenids but also their habit of drinking exclusively from the Choaspes.

The application of this tradition to the Arsacid kings is at any rate clear from Lucan's contemporary Pliny the Elder, even if the author mentions two river names rather than one. In a report that echoes Herodotus, Pliny writes (HN 31.35):

Pliny's addition of the second river represents only a slight discrepancy. It can perhaps be explained by Potts's argument that ‘Eulaeus’ was the pre-Achaemenid hydronym for the Choaspes, which was renamed after Susa fell under Persian rule—a matter of nomenclature that led to confusion among commentators both ancient and modern.Footnote ¹² In any event, while Pliny alone treats the Eulaeus as a separate source of royal water, many authors from the first century c.e. through Late Antiquity and the Byzantine period echo the Choaspes tradition, sometimes with minor variations. The kings who drink exclusively from the river are usually called ‘Persian’, an ethnonym that by the third century c.e. could refer to the Achaemenids, the Arsacids, the Sasanians or an amalgamation of all three dynasties and the people they ruled.Footnote ¹³

One might object to the notion that Lucan's Pompey is noticeably ignorant of the Choaspes tradition by adducing his use of the word populi; Pompey, it could be argued, is referring not to the family of kings that dominates the East but to the various ethnic groups that live in their empire. Perhaps Lucan has modelled the lines on Tityrus’ exclamation in Virgil's first Eclogue (1.61–3):

Tityrus speaks of ‘the Parthian’ in general, and the logic of the passage assumes that Parthians ordinarily drink from the Tigris.Footnote ¹⁴ The speaker does not appear to have an Arsacid king in mind but rather a typical inhabitant of the Parthian empire.Footnote ¹⁵ Where Pliny explicitly denies that the Arsacids drink from the Tigris, Virgil seems to think that their subjects did. With the word populi, Lucan may simply draw on the Roman poetic tradition of ‘designat[ing] barbarian peoples by naming the rivers they dwelt near and hence were supposed to drink from’.Footnote ¹⁶

This explanation cannot excuse Pompey's error, however, and there are two reasons to hold him to account. First, Pompey is sending Deiotarus to address not a generic Parthian but rather the ‘proud Arsacid’ (superbo Arsacidae) at the head of the realm.Footnote ¹⁷ Second, Lucan is unique among Latin poets in his use of the patronymic Arsacides (‘son of Arsaces’, the progenitor of the Arsacid line). Aside from one later reference in the Punica of Silius Italicus, the Bellum Ciuile is the only Latin poem to describe the Parthian kings as Arsacidae.Footnote ¹⁸ In the paired speeches that follow the Deiotarus passage, both Pompey and Lentulus refer not only to the various ethnic groups that inhabit the Parthian empire but also to the Arsacids (8.233, 8.307, 8.409). Indeed, one of Lentulus’ arguments against a Parthian alliance specifically focusses on the habits of the ruling family: the Arsacid king's polygamy and his incestuous relations with his mother and sisters are said to endanger Cornelia, who (in Lentulus’ view) must not be exposed to such sexual depravity.Footnote ¹⁹ The narrator of the epic also refers to the Arsacidae in the proem and in his digression on Alexander in Book 10 (1.108, 10.51). Lucan does speak of ‘Parthians’ in general, to be sure, and he deals in the Roman stereotypes of this people that are common in Latin poetry.Footnote ²⁰ But his epic is unparalleled in its focus on the Arsacid dynasty and on the king at its head. It is this king who will determine the outcome of Pompey's embassy.

Because of his express concern with the Arsacid ruler, the phrasing of Pompey's appeal to ‘the people who drink the Euphrates and the Tigris’ sends up a red flag. The Arsacidae are the main referent of the populi evoked in this statement—but the Arsacids do not drink from either river. A long literary tradition held that the kings of Persia drank only from the Choaspes or, as Pliny relates, only from the Choaspes and the Eulaeus. As a contemporary of Lucan, Pliny is good evidence that this tradition was current in the Neronian period, and that it had transferred from the Achaemenid to the Arsacid kings.Footnote ²¹ For internal or external audiences with knowledge of the Choaspes tradition, Pompey could hardly have chosen a less appropriate way to initiate contact with the head of the Parthian empire.

What effect does this misstatement have on a reader who is well versed in Persian ethnography? On a general level, the error further supports a characterization of Pompey that several scholars of Lucan have advanced: at this point in the epic, the Republican leader is geographically and morally adrift, out of his element and increasingly desperate as power slips away. His intention to ally with Parthia marks a nadir, as many have argued.Footnote ²² In his speech to the Republicans advocating this course of action, Pompey will echo the words ‘Rome, favour my undertakings’ (Roma, faue coeptis) first uttered by Caesar as he crossed the Rubicon.Footnote ²³ With the redeployment of this phrase, Republican ideals have all but vanished from view. Pompey shows himself ready to stoop to his tyrannical enemy's level, and his overtures to the Arsacids suggest a flirtation with eastern despotism that little becomes a hero of the Roman Republic.

But Pompey's misstatement about the drinking habits of the Arsacids shows that his character is marred by ignorance as much as by immorality; disoriented by Pharsalus and lost in the East, he is blind to the danger of his position and to the imminent threat of betrayal. Tracy's recent interpretation of the Deiotarus episode has shown how the passage highlights ‘Pompey's pathetic naiveté and misplaced trust in the people around him, particularly easterners’ in view of the Galatian king's later accommodation with Caesar—hardly the action of a supporter whom Pompey calls the ‘most trustworthy of kings’ (fidissime regum, 8.212).Footnote ²⁴ In the end, neither Deiotarus nor Ptolemy XIII will prove to be a faithful eastern client, and Pompey's inability to tell friend from foe amidst the new realities of the post-Pharsalus world will lead to his own death and to a mortal blow against Republican liberty. The shortcomings of Pompey's worldliness, judgement and knowledge—soon to prove so deadly to him—are all adumbrated in his unfortunate remark.

Pompey's apparent ignorance of the East is an especially dire indication of his fortunes, because it is precisely this part of the world that many earlier passages have established as the base of his power. For the narrator of the epic, it was Pompey who added eastern wealth to the treasury of Rome (3.165–7). The catalogue of Pompey's forces in Book 3 reviews a vast array of eastern peoples, some impossibly remote, who muster to fight for him. As Bexley shows, Lucan's catalogue anchors Pompey's might in the eastern part of the world as it anchors Caesar's in the west.Footnote ²⁵ Moreover, the passage draws on both riverine geography and ethnography to demonstrate Pompey's far-reaching influence; rivers from the Tigris and the Euphrates to the Ganges and the Hydaspes feature prominently, as do ethnographic remarks on the sugar-cane drinking of the Indians and the hair accessories of the Arimaspians.Footnote ²⁶ When Pompey begins his post-Pharsalus initiatives with a misstatement that reveals his ignorance on a point of geographic and ethnographic detail, and moreover a point that concerns a river, the sense of awe and confidence that the catalogue inspired in the extent of his power is undermined. Pompey's knowledge of the East is limited, it turns out, and so too, one senses, is his authority there.

The foundering of Pompey's leadership upon the waters of the Tigris and the Euphrates is not merely a character flaw, however: his personal failure reflects greater challenges to Rome's universal aspirations in the Parthian East. When Pompey calls the Arsacid kingdom an orbis alius in his speech before the Republicans, he draws on an imperial literary tradition of representing Parthia not just as a political territory outside of Roman jurisdiction but as an entirely different world, or at least a part so remote as to be essentially inaccessible.Footnote ²⁷ Pogorzelski has shown how the eighth book of Lucan's epic presents a worldview that deviates markedly from the political geography of the proem, where Rome is accorded a place at the centre of the cosmos. By contrast, the treatment of Parthia in the eighth book configures the Arsacid kingdom as an imperial counterpart, a sovereign eastern world that undermines Roman pretentions to the centrality of their city and the universality of their empire.Footnote ²⁸ The defeat at Pharsalus has not merely destabilized the authority of Pompey, the former master of the East. It has limited the horizons of Roman knowledge and power, which can no longer penetrate the Parthian world beyond the Euphrates. Pompey's failure to identify the Choaspes as an Arsacid drinking-source thus underscores his personal ruin even as it points to the autonomy of a vast eastern realm, dominated by Parthia, that Rome can neither comprehend nor rule.

Though Pliny is the best source for the currency of the Choaspes tradition during Lucan's lifetime, the royal status of the river was neither a mere curiosity of historical geography nor a triviality unsuitable for poetry. As noted above, Tibullus called the stream a regia lympha in a passage that drew its vocabulary from Herodotean geography and ethnography.Footnote ²⁹ Moreover, no less an epic successor than John Milton would allude to the Choaspes as a royal water-source. In Paradise Regained, Satan calls the river ‘the drink of none but Kings’ in an extended description of the lands that belonged to the Persian and Parthian empires.Footnote ³⁰ This ethnographic detail may be specific, then, but it is hardly obscure. Pompey could perhaps be forgiven for not reading Pliny. But in his utter ignorance of the Choaspes tradition—long and well attested in a wide array of Greco-Roman texts, including poetry—he exhibits a lack of erudition that highlights the eastern limits of Roman rule in the wake of civil war.