59 in the avesta the ethnonym iiaona- occurs four times, once in Yt 19,87 and thrice in Yt 9,30–31. 1 these pas- sages have all been edited by Hintze (1994: 361–363). in all these occurrences reference is made to the so- called “battle of the religion” fought by king Vīštāspa (MP Wištāsp), Zoroaster’s patron, against arəja.aspa (MP arjāsp), the iiaona. Descriptions of this battle are found in the Middle Persian Ayādgar ī Zarērān (Monchi-Zadeh 1981) and in the Šāhnāma (Mohl 1855: 366–427). 2 the battle fought by Vīštāspa against arə- ja.aspa, king of the iiaona, the so-called “battle of the religion” is one of the very few episodes of iranian epics to be attested throughout iranian literary history. in fact, it is found in the Younger avesta, in Pahlavi literature and in Ferdowsi’s masterpiece. Moreover, the Ayādgar ī Zarērān is, together with the Draxt ī Asūrīg, the only Middle Persian work to preserve memory of an earlier Parthian version, here attested particularly in direct speech. the Middle Persian version as we have it has probably reached its final form in the 5 th century (Pagliaro 1925: 554). Unfortunately, neither the Middle Persian work nor Ferdowsi’s masterpiece provide us with any interesting information about the Xyōn. Quite on the contrary, in the Ayādgar ī Zarērān it is only said that the Xyōn were Wištāsp’s deadly fiends, while the Šāhnāma removes this ethnonym considering arjāsp to be a turanian king. the only geographical information found in the Ayādgar ī Zarērān is in § 19, where it is said that the battle will take place near Hutōs ī Razwar and Marw ī Zarduxštān, thus setting the events in the eastern part of the iranian world. as we shall see in what follows, other passages found in Pahlavi literature and in the Middle Persian commentaries to the avesta may prove more informative. Before presenting the texts, a short reference to a problem which has been widely discussed in the 20 th century needs to be made. the close similarity between av. iiaona- and MP Xyōn has opened a debate on the identity of the avestan iiaona and on their relationship to the MP Xyōn. Scholars are divided in two main camps. the position held by the first one was voiced by Markwart (1901: 50), who thought that the battles again the Xyōn in Sasanian times left such a deep impression that their name found its way into the avesta, substituting the original name of Vīštāspa’s foes. 3 this view is shared by Maenchen-Helfen (1959: 227–228, n. 10) and, though not outspokenly, by Ghirshman (1948: 115–116). Herzfeld took a similar position since he also thought that the avestan text may have been manipulated in Sasanian times, more specifically during the reign of Šābuhr ii; however, his hypothesis that iiaona- may have been substituted to an original Yaona- / 1 Yt. 17, 50 –51 = Yt. 9, 30–31. 2 For a description of the events according to the various sources see Jackson 1899: 102–123. Neither etymology nor exact mean- ing of this ethnonym are ascertained. However, Pirart’s proposal (1992: 113, see also tremblay 2001: 186) to derive it from se- Hu-no-, cf. Skr. syūna- “sack” and NP yūn “saddle-cloth”, is attractive, not least because it may connect iiaona- to the world of nomadic horse riders. another attempt to explain the etymology of the name iiaona- is found in Bailey 1972: 18–21, on which see Hintze 1994a: 362–363. Quite clearly, i share the opinion that both this ethnic name and the people that it defines stand good possibilities to be of indoeuropean origin, cf. Maenchen-Helfen 1959: 236–238 and Harmatta 2002: 74–75. 3 Markwart 1901: 50: “Dem eindruck, den dieses Volk bei den iraniern hinterlassen haben muss, entspricht es denn auch, dass ihr Name sogar ins awesta eindrang und den der dort ursprünglich genannten Feinde des Kawi Wištāspa, des Beschützers des Za- raθuštra völlig verdrängte“. later Markwart seems to have taken a different position, as remarked by Gnoli 1967: 117, with bib- liography. C arlo G. C ereti ´ Xiiaona- and Xyōn in Zoroastrian texts