Yirmibeşoğlu was first Chief of Staff, then Chief of the Turkish Armed Forces' Special Warfare Department ("Özel Harp Dairesi") between 1974 and 1976 and commanded the special forces activities in Northern Cyprus in the eve and initial stages of the Turkish Operations in July and August 1974. In 2010 Yirmibeşoğlu reported to the television news channel Habertürk TV that Turkey burned a mosque during the Cyprus conflict in order to foster civil resistance against Greeks on the disputed island, and that their rules of war included "false flag" acts, engaging in acts of sabotage made to look as if they were carried out by the enemy.