Well you may have thought that the United States kept its nose pretty clean in the 1800s with a mere four wars. In the 1900s, the number crept up to five. Here are the answers that the USCIS interviewer might be hoping for:
- World War I
- World War II
- Korean War
- Vietnam War
- (Persian) Gulf War
You only need to answer one, so my advice is to go with WW2 as it appears in other questions too.