In the 1930s, the Great Depression and bitter memory of losses in WWI shifted American public opinion toward isolationism. However, support for isolationist groups such as the America First Committee rapidly declined with the Japanese attack on Pearl Harbor, although several smaller religious and socialist groups continued their opposition to war.
British philosopher Bertrand Russell, taking a position of relative pacifism, argued that defeating Nazi Germany was a unique circumstance in which war was the lesser of possible evils.
Albert Einstein wrote: “I loathe all armies and any kind of violence; yet I’m firmly convinced that at present these hateful weapons offer the only effective protection.”
The U.S. government allowed sincere objectors to serve in noncombatant military roles. However, those draft evaders who refused any cooperation with the war effort were often imprisoned.