We have seen in Chapter 2.2 that the rebellion of Thomas the Slav had already started in the reign of Leo V, c. 819-820, as stated in the Latin version of the letter Michael II of Amorion wrote to the western emperor Louis after the end of the war. Contrary to former studies, we concluded that in this respect the information provided by the letter is to be trusted as it is corroborated by other contemporary sources. Now, there is another controversial point in the Letter to Louis that needs to be considered here as it is of crucial importance in understanding the outbreak of the war: the statement that Thomas was a Christian renegade who lived among the Arabs after he fled from Byzantium during the reign of the empress Eirene (797-802) until the very beginning of his usurpation.