The US Civil War (1861-1865); since we fought ourselves!
The most Americans died in Vietnam which was also the longest war that America was involved in.
For Americans the civil war had the most fatalities.
Both sides, North and South, were considered Americans. So the total number of deaths were all Americans.
The US Civil War (1861-1865), for the simple reason that Americans were killing Americans.
World War II. Over 16 million Americans served.
WW2.
Second World War, in which over 16 million Americans were inducted into the Armed Forces.
Neutral
↓yes↓
The largest number of Americans served in the armed forces during World War II, which lasted from 1941 to 1945. Approximately 16 million Americans were mobilized for military service during this conflict, making it the most significant military engagement in U.S. history in terms of troop participation. The war had a profound impact on American society and the global order that followed.
Japanese Americans
Americans wanted to withdraw into an isolationist position.