Menetrey was born on 19 August 1929, in Hollywood, California, to a Swiss immigrant father and American mother.

In Vietnam, his first assignment was as Deputy chief of Staff of the 1st Cavalry Division, and then was given command of the 2nd Battalion, 28th Infantry, a unit that had been badly mauled by recent combat.

During this assignment, Menetrey received the Distinguished Service Cross for heroism against Viet Cong forces near Bến Cát.

After Vietnam, he attended the National War College, and then was assigned to the Office of the Coordinator of Army Studies, working for Vice Chief of Staff General William E. DePuy, and assisting in developing policies for transition to an all volunteer force.

His next assignment was as Deputy Commander, Combined Arms Development Agency, where he helped lay the groundwork for the National Training Center.