After the fall of the Soviet Union, 366th regiment was pulled out of Stepanakert in March 1992 and Ohanyan joined Nagorno-Karabakh's newly formed army, playing a major role in the First Nagorno-Karabakh war against Azerbaijan. In May 1992, Ohanyan participated in the capture of his hometown of Shushi, one of the most significant victories achieved by the Armenian side. He led a force of 400 men against the fortified town from the southwestern direction. He was seriously wounded in action near Chldran, Martakert district in September 1992, with his leg amputated as a result. Following treatment, Ohanyan re-joined the military.