The Eastern Frontier consists of seven chapters, preceded by a list of abbreviations (p. viii), list of maps (p. ix), acknowledgements (pp. x–xi), introduction (pp. 1–15), and followed by conclusions (pp. 197–200), notes (pp. 201–58), bibliography (pp. 259–81) and an index (pp. 282–96). The book is graphically well done with a good proportion between page size, font and line spacing; the maps, all in black and white, are of good quality and of an appropriate size. The numerous and precise notes are placed at the end of the text and not at the foot of the page: this choice, I presume editorial, forces the reader to move from one end of the volume to the other, weighing down the rhythm of reading: on the other hand this allows the font size of the notes to be kept as in the body of the text, makes the consultation of notes more agile and at the same time keeps the page layout elegant.

Haug’s work concerns what was once the eastern frontier of the Sasanian Empire and after the Arab conquest the eastern frontier of the Umayyads and Abbasids. Frontier is an extremely interesting concept and one can look at it from several points of view: we have linguistic, ethnic, political and religious frontiers. A frontier may also be the point of contact between two different ways of life, for example sedentary and nomadic. All these aspects of the frontier concept cannot be superimposed: a linguistic frontier hardly coincides perfectly with the political, ethnic or religious one. This is valid both in the contemporary world and in antiquity. The eastern frontier presents many of these different overlapping interpretative aspects: it was a political frontier that separated the Iranian empires from what lay beyond; it has long been a frontier that separated the nomadic world from the sedentary one; a religious frontier as it delimited the space of Zoroastrianism in the pre-Islamic period, later that of Islam; ethnic because it marked the border between Iranian and Turkish peoples.

Haug clarifies right from the introduction the value he intends to assign to the eastern border: from an area where different cultures meet up to the conceptualization of the border among medieval geographers. But more than a real dividing line, the eastern border is a strip in which every event inevitably has repercussions on both sides (drastic changes on one side of the frontier create a domino effect that shifts equilibrium dramatically from one direction to the next; p. 3). The frontier is therefore a place in constant movement, but also a place where a balance is constantly sought: when this balance jumps, the repercussions are immediate on both sides.

The title of the first chapter is “The Gate of Iron: Conceptualizing the Eastern Frontier in Medieval Geographic Literature” (pp. 18–41). This chapter opens with a detailed review of the identifications of the Iron Gates. It is well known that this term has been used to indicate various places, often very distant from each other, starting from the shores of the Caspian Sea to Central Asia. In reality, all this is used by the author to demonstrate that the perception of the eastern border by medieval Arab geographers was far from being perfectly defined. What appears evident from the work of the Arab geographers of the ninth and tenth centuries are a large Khurāsān and a Transoxiana which have no well-defined borders at all. What is said in this first chapter opens the way for a flashback that offers the starting point for the second chapter, “Shaping the Eastern Frontier: The Sasanian Empire and Its Eastern Neighbours” (pp. 43–70). This chapter offers the author the opportunity to consider Sasanian politics in relations with the regions of the empire.

The author points out that the struggle between the Sasanians and the Romans/Byzantines did not at all prevent a constant commitment on the eastern front, where the border was controlled and, on several occasions, fortified as much as possible. Over the centuries, new peoples appeared on the eastern borders and represented a challenge for the Sasanian Empire (the frontier was ever changing as new peoples moved into the frontier zone who posed different challenges to Sasanian authority; p. 70). The title of the third chapter is “The Arab-Muslim Conquest and the Late Antique Imperial Shatterzone” (pp. 71–98). This chapter examines the conditions of the eastern regions of the Sasanian Empire during and immediately after the Arab conquest. In particular, the focus is on the relationship between the local lords and the newcomers, but attention is given also to the Sasanian attempt to maintain power in the eastern regions. It is also emphasized that the Arab conquest in these regions represented a forced inclusion in the Arab–Muslim social categories and it was not a process of integration of populations and local powers within the new established order (conquered populations were forced into Arab–Muslim social categories instead of integrating into the newly formed empire with their own existing social networks, p. 97).

The fourth chapter examines “The Frontier Beyond the Caliphate: Khurāsān and the Second Fitna” (pp. 99–110). The center of attention of this chapter is the attempt of further territorial extension and the profound lack of unity within the Arab forces, which overlaps with the different local oppositions. All this is beyond the rhetoric of the conquest that we meet in several sources. The picture that emerges is enormously complex and clarifies the reasons why these frontier territories were often the center of rebellions against central power (in the frontier zone, multiple layers of division had opportunities to overlap and create new alliances that could work to advance individual interests; p. 110). The title of the fifth chapter is “Extending the Frontier: The Umayyads in Sogdiana and Beyond” (pp. 111–37). The next phase is analyzed here, the one that will actually lead to the incorporation of the eastern territories within the structures of the empire. This process had considerable repercussions along the entire eastern frontier and in a certain sense Sogdiana became a desired territory both by the Umayyad Caliphate and by the Western Türk Khāqānate (this chapter examines Sogdiana as a meso-imperial space caught between and desired by both the Umayyad Caliphate and the Western Türk Khāqānate; p. 113). The author clearly underlines at the end of the chapter that the successes and failures of Umayyad politics in the region are the result of a balance between Arab and Turkish unity and that both contenders were subject to a phenomenon of fragmentation due to the presence of different factions (p. 136).

The sixth chapter is “The Unsettled Frontier: The Abbasid and Other Revolutions and the Eastern Frontier” (pp. 139–67). Here the consequences of the conquest and integration of the eastern territories are examined: these territories were affected by a long series of revolts from the mid-eighth century. Now the type of revolt changes and it no longer involves just one ethnic group, but affects all factions both within the Arab world and at local level: great attention is paid to the Abbasid revolution that, starting from Khurāsān, led to the overthrow of the Umayyad Caliphate. Under the Abbasids there was a new attempt to move the eastern frontier further beyond the Jaxartes, but there was still a lack of a real union between all the territories that faced the eastern frontier of the empire. The title of the seventh chapter is “Unifying the Frontier: The Formation of Greater Khurāsān” (pp. 169–95). Here the author examines the formation of the so-called great Khurāsān: this region became independent under the Samanids. The chapter also examines some of the aspects that will later favor the passage of the region under Turkish control. Khurāsān under the Ghaznavid rule and in the moment of the passage under the Seljuks was the subject of a work by B. N. Zachoder which, unfortunately, was published in 1945 in Voprosy istorii in Russian and never got the circulation it deserved.

Overall, Haug’s work presents a very accurate and complete picture of the subject. The author makes it easier to move around the volume through a constant reminder of what has been said in the previous chapters and he constantly underlines what are the purposes of the chapter. The language is fluent and always precise. The transcriptions follow always the adopted system. Notes are good and numerous (some 1,014); the bibliography includes over 500 titles with excellent coverage of sources. It is therefore engaging, useful and high-level reading for anyone interested in the eastern regions of the Sasanian Empire, the latter part of the Umayyad caliphate and then of the Abbasids. The author demonstrates that he knows how to move with agility and precision on a subject that requires considerable historical and linguistic skills, but above all he is able to render a complex subject into a highly informative and rewarding read.