He enlisted in the U.S. Marine Corps in 1944 and completed officer training at Quantico and was assigned command posts with the 81st Rifle Company, the 1st Marine Regiment, and the 8th Marine regiment before he deployed to Vietnam with the 3rd Marine Regiment.
On February 28, 1976, while at a small outpost near Camp Carroll, Lieutenant Colonel Ohanesian and his men came under attack. Unable to gain the upper hand, Lieutenant Colonel Ohanesian ordered a withdrawal, and while carrying the last of the wounded Marines out of the area was hit by mortar fire. Because of the intensity of the firefight, the evacuation was impossible and Lieutenant Colonel Ohanesian died in the early morning hours of March 1, 1967. He rests at Arlington.