Battle of the Oinousses Islands (Turkish: Koyun Adaları Muharebesi) was a medieval naval engagement in the Aegean Sea.
Tzachas was a Turkish seaman who founded a quasi-independent principality around Smyrna (modern İzmir) in the late 11th century.
He founded a maritime principality around Smyrna and he frequently campaigned on the Byzantine islands in east Aegean sea.
However upon learning about an approaching Byzantine fleet under the command of Niketas Kastamonites, he decided to fight.
[2] After the battle Tzachas annexed the islands of Chios and Samos.