The Schechter Letter, also called the Genizah Letter or Cambridge Document, was discovered in the Cairo Geniza by Solomon Schechter in 1912. It is an anonymous Khazar letter from the Genizah of Cairo, discussing several matters including the wars of the early 940s, involving the Byzantine Empire, the Khazar Khaganate, and Kievan Rus'. Scholars have debated its authenticity. The Letter The Schechter Letter has been interpreted as a communique from an unnamed Khazar author to an unidentified Jewish dignitary. Some believe that the Schechter Letter was addressed to Hasdai ibn Shaprut by a Constantinopolitan Khazar after his first, unsuccessful attempt to correspond with the Khazar king Joseph (see Khazar Correspondence). However recent historiography has noted the names echoing Jewish mystical traditions and lack of any corroborating historical sources to its account may place it in a tradition of fantastical writing about the lost tribes of Israel. The Letter was included in the Genizah Collection donated by Schechter to Cambridge University in 1898. Most of the folio is unreadable and only two surviving blocs of text exist. This makes identifying the precise nature of the letter, communique or legend unclear. The conversion text The Schechter Letter contains an account of the Khazar conversion that differs from that of the Khazar Correspondence and the Kuzari. In the Schechter Letter account, Jews from Persia and Armenia migrated to Khazaria to flee persecution, where they mingled with the nomadic Khazars, eventually assimilating almost totally. Then a strong war-leader arose (in the Schechter Letter, he is named Sabriel), who succeeded in having himself named ruler of the Khazars. Sabriel happened to be remotely descended from the early Jewish settlers, and his wife Serakh convinced him to adopt Judaism, in which his people followed him. What follows in the Letter is largely lost except for a few fragments. The account of the Khazar kingdom matches up with no Muslim, Jewish or Byzantine source from the period regarding wars of migration. It also differs radically from every other alleged source on the Khazar conversion to Judaism and in its naming of the ruling class. The names of the figures involved, Sabriel being the name of an angel in the Jewish mystical tradition, Serah being a biblical figure and the claim of descent from the tribe of Simeon whose demise is chronicled in the bible, strongly indicate the text is an unreliable source and heavily influenced in a