Such letters issued by newly made caliphs calling on infidel kings to renounce their beliefs and submit to Islam are common and follow the pattern of Muhammad’s missives to Heraclius and others. Leo responded with his own letter, “the first known Byzantine text which refutes Islam, and it shows knowledge of the subject much wider than that of other contemporary polemicists.”60 In it, Leo, “who was as zealous in his Christian faith as Omar was in his, refuted Islam on the basis of the Christian Gospel as well as on the basis of the Koran.”
