 Employing Christian craftsmen, he built a fleet, with which he captured Phocaea and the eastern Aegean islands of Lesbos (except for the fortress of Methymna), Samos, Chios and Rhodes.A Byzantine fleet under Niketas Kastamonites was sent against him, but Tzachas defeated it in battle.Some modern scholars have speculated that his activities during this time may have been in conjunction, and perhaps even coordination, with two contemporary Byzantine rebels, Rhapsomates in Cyprus, and Karykes in Crete.