[1] John had a brother, Andronikos, who was also a prominent general – he led an army against the city of Amaseia in 1176 and was killed by the Seljuq Turks; they displayed his severed head during the Battle of Myriokephalon shortly afterwards.[6] John Komnenos Vatatzes enters contemporary sources as a senior general in the 1170s; it is certain that he served in lesser military capacities before being appointed to high command, but no record of his activities has survived.He undoubtedly had a military apprenticeship under his father Theodore, also a prominent general, who undertook the siege of Zemun on the Hungarian frontier in 1151, and captured the city of Tarsus in Cilicia in 1158.Following a truce which allowed the Byzantine army to retreat from Turkish territory, Manuel failed to implement all the conditions, particularly the destruction of border fortresses, demanded by the Seljuq sultan Kilij Arslan II as a prerequisite for a cessation of hostilities.The sultan reacted by dispatching a substantial Seljuq cavalry army, numbering about 24,000 men, to ravage Byzantine territory in the Meander Valley in western Anatolia.[15] When Vatatzes is again mentioned in the sources, in 1182, he is holding very high office: he was both megas domestikos, the commander in chief of the Byzantine army, and governor of the important Theme (province) of Thrace.[16][17] The city of Adrianople was both the seat of the government of Thrace and the centre of the landholdings of the Vatatzes family, and John is recorded as building and endowing fine almshouses and hospitals there.