1. Civil War (1861-1865): Approximately 620,000 American soldiers and civilians died.
2. World War II (1941-1945): Over 400,000 American soldiers and civilians lost their lives.
3. World War I (1917-1918): Approximately 116,000 American soldiers died.
4. Korean War (1950-1953): Around 36,500 American soldiers were killed in combat.
5. Vietnam War (1955-1975): Almost 58,200 American military personnel died in the conflict.
6. Revolutionary War (1775-1783): Historians estimate that between 25,000 and 70,000 Americans lost their lives during this war.
7. War of 1812 (1812-1815): Approximately 2,260 Americans died in combat.
8. Mexican-American War (1846-1848): Around 13,283 American troops died in battle or due to disease.
9. Persian Gulf War (1990-1991): 248 American soldiers were killed.
10. Iraq War (2003-2011): 4,424 American soldiers died in this war.
It's worth noting that the above figures are estimates and can vary depending on the source.