Like his father he was appointed to the office of megas doux, the commander-in-chief of the Byzantine navy and governor of the provinces of Hellas, the Peloponnese and Crete.
[9][10] Andronikos next appears, along with his brother Alexios, in the course of Manuel I's attempts to settle the dynastic succession in the Kingdom of Hungary in his favour after the death of King Géza II in 1161.
[13][14] Stephen IV's death transformed the conflict into a plain Byzantine–Hungarian war over Sirmium and Dalmatia; both areas were re-occupied by the Hungarians in 1166, after achieving major successes against the imperial forces.
The ensuing Battle of Sirmium resulted in "the most spectacular military victory [...] during Manuel's reign" (Paul Magdalino), thanks in large part to the crucial intervention of the reserves under Andronikos himself.
[21][22] The campaign, planned between the two Christian monarchs possibly since the marriage of Amalric with Manuel's great-niece Maria in 1167, would not only end in failure, but also lead to the establishment of the energetic Saladin in the place of the moribund Fatimid government as ruler of Egypt, in what would prove a major turning-point of the Crusades.
[23] Manuel mobilized a large force, well beyond what he was obliged, according to the chronicler William of Tyre: 150 galleys, sixty horse-carriers and a dozen dromons specially constructed to carry siege engines.
After defeating a small Egyptian scouting squadron near Cyprus, Kontostephanos arrived at Tyre and Acre in late September to find that Amalric had undertaken no preparations whatsoever.
[26] The discipline and cohesion of the Byzantine army almost instantly disintegrated after the news of the peace deal were announced, with troops burning the engines and boarding the ships in groups without order.
[29] In April 1172, Kontostephanos set sail, but the Venetians were forewarned by the astrologer Aaron Isaakios, one of Manuel's confidantes, and hastily abandoned Chios.
Doge Vitale II returned his fleet to Venice on 28 May, but the losses suffered and the failure to gain any concrete objective led to his lynching by the angry mob.
[30] Manuel attacked the Seljuk Sultanate of Rûm in 1176, with the intention of taking its capital, Konya, and destroying Turkish power in Anatolia.
The Seljuk sultan Kilij Arslan II ambushed Manuel's impressively large army as it moved through the pass of Tivritze in mountainous border region between the two states.
In the ensuing Battle of Myriokephalon parts of the Byzantine force were very badly mauled; however, Andronikos Kontostephanos managed to get his division, bringing up the rear, through the pass with few casualties.
He was dissuaded from continuing with the expedition by the refusal of Count Philip of Flanders, and many important nobles of the Kingdom of Jerusalem, to actively co-operate with the Byzantine force.