In how many wars has the United States employed the recruitment method that was protested by Thomas E. O'Donnell?
Thomas E. O'Donnell:  He was a public opponent of the draft, so he was promptly arrested. Conscription in the United States: Conscription in the United States, commonly known as the draft, has been employed by the federal government of the United States in four conflicts: the American Civil War, World War I, World War II, and the Cold War (including both the Korean and Vietnam Wars).
four