There are half a million dead Civil War Soldiers and several million from WWI and WWII who would take issue with your point.
"For more than 50 years, Selective Service and the registration requirement for America's young men have served as a backup system to provide manpower to the U.S. Armed Forces.
President Franklin Roosevelt signed the Selective Training and Service Act of 1940 which created the country's first peacetime draft and formally established the Selective Service System as an independent Federal agency.
From 1948 until 1973, during both peacetime and periods of conflict, men were drafted to fill vacancies in the armed forces which could not be filled through voluntary means.
In 1973, the draft ended and the U.S. converted to an All-Volunteer military.