After the 838 Sack of Amorium, the hometown of the emperor Theophilos () and his Amorian dynasty, the caliph al-Mu'tasim () took more than forty Roman prisoners. These were taken to the capital, Samarra, where after seven years of theological debates and repeated refusals to convert to Islam, they were put to death in March 845 under the caliph al-Wathiq (). Within a generation they were venerated as the 42 Martyrs of Amorium. According to their hagiographer Euodius, probably writing within a generation of the events, the defeat at Amorium was to be blamed on Theophilos and his iconoclasm. According to some later hagiographies, including one by one of several Middle Byzantine writers known as Michael the Synkellos, among the forty-two were Kallistos, the "doux" of the Koloneian "thema", and the heroic martyr Theodore Karteros.