Alexios Mosele ( Caesar ) Alexios Mosele ( ) or Musele / Mousele ( Μουσελέ ) was a Byzantine aristocrat and general , chosen by Emperor Theophilos ( r . 829 – 842 ) for a time as his heir , betrothed to his daughter Maria and raised to the supreme dignity of " Caesar " . He campaigned in the Balkans , recovering territory from the Slavs , and fought with some success in Sicily against the Arabs . Recalled to Constantinople on suspicion of plotting to usurp the Byzantine throne , he was imprisoned but later pardoned and allowed to retire to a monastery , where he spent the remainder of his days . Biography . Alexios was possibly the son or the grandson of the general Alexios Mosele , who had been active under Constantine VI ( r . 780 – 797 ) , although Byzantine chroniclers record that he was descended from the Krenites family . A brother named Theodosios , who held the high court title of " patrikios " , is also recorded . Sometime between 836 and 839 , Alexios was engaged to the princess Maria , Emperor Theophilos ' s youngest and favourite daughter , despite the fact that she was an infant . Theophilos had no male heir at the time , and this move was evidently intended as marking out Alexios as his heir apparent . He was progressively promoted to " patrikios " and " anthypatos " , then to " magistros " and eventually to " Caesar " . He was the only person known to have been promoted to the rank during Theophilos ' s reign , and may indeed have been raised to it as early as 831 , when the presence of an unnamed " Caesar " is attested at an imperial triumph . Alternatively , it may be a reference to another , otherwise unknown , holder of the title , who probably died shortly after . In summer 836 , Mosele , recently promoted to " Caesar " , was dispatched with an army against the Bulgars in Thrace . Instead of confronting them , however , he focused on recovering for the Byzantine Empire the coastal strip between the rivers Nestos and Strymon , which had been abandoned to the local Slavs by the Byzantine - Bulgarian Treaty of 816 . In this way , he restored the direct land connection between Thrace and Thessalonica , the Empire ' s major Balkan city . After founding a new city , named " Caesaropolis " after himself , he returned to Constantinople . Alexios may have participated in Theophilos ' s successful campaign against Melitene in 837 , as he is recorded to have participated in the triumph that followed the emperor ' s return . This , however , is disputed by some scholars . In 838 , Mosele was sent on an expedition against the Arabs in Sicily . There , he achieved a number of successes , forcing the Arabs to raise their siege of Cephaloedium , and inflicted several defeats upon their forces . His forces , however , were insufficient to evict the Arabs altogether from their holdings in the western part of the island , and in late 838 he suffered a defeat at the hands of fresh Arab reinforcements . At the same time , Alexios ' s betrothed Maria died , age four , and his connection to Theophilos became tenuous . He was also accused by some Sicilians of colluding with the Arabs and planning to become emperor himself . To avoid forcing his " Caesar " into a corner , Theophilos sent Theodore Crithinus , Archbishop of Syracuse , to recall him under guarantees of personal safety . Nevertheless , upon his arrival in the capital , Alexios was stripped of his titles , beaten , and imprisoned . Theodore Crithinus publicly confronted the emperor for his breach of his word at the Church of St . Mary of Blachernae , but the enraged Theophilos had him beaten and exiled as well . Soon , however , the Patriarch John the Grammarian too publicly berated Theophilos . The emperor relented , released both Theodore and Alexios , and restored the latter to his rank and property . His relations with the emperor , however , cooled considerably , particularly after the death of Maria and the birth , in 840 , of Theophilos ' S son , Michael III ( r . 842 – 867 ) . By 842 , Mosele had retired to a monastery at the quarter of " ta Anthemiou " in Chrysopolis , which he himself had founded . Nothing is known of him thereafter .