One of the five Syriac manuscripts, dated to the 18th century, has a version of the Syriac legend that has been generally dated to between 629 AD and 636 AD. There is evidence in the legend of ""ex eventu" knowledge of the Khazar invasion of Armenia in A.D. 629," which suggests that the legend must have been burdened with additions by a redactor sometime around 629 AD. The legend appears to have been composed as propaganda in support of Emperor Heraclius (575–641 AD) shortly after he defeated the Persians in the Byzantine-Sassanid War of 602–628. It is notable that this manuscript fails to mention the Islamic conquest of Jerusalem in 636 AD by Muhammad's (570–632 AD) successor, Caliph Umar (590–644 AD). This fact means that the legend might have been recorded before the "cataclysmic event"` that was the Muslim conquest of Syria and the resulting surrender of Jerusalem in November 636 AD. That the Byzantine–Arab Wars would have been referenced in the legend, had it been written after 636 AD, is supported by the fact that in 692 AD a Syriac Christian adaption of the "Alexander romance" called the "Apocalypse of Pseudo-Methodius" was indeed written as a response to the Muslim invasions and was falsely attributed to St Methodius (?–311 AD); this "Apocalypse of Pseudo-Methodius" equated the evil nations of "Gog and Magog" with the Muslim invaders and shaped the eschatological imagination of Christendom for centuries.