Which american president saw active service in both the first and second world wars?

The would be Dwight Eisenhower. After graduating from West Point in 1915, Eisenhower served as a lieutenant. Although he didn't see any combat in WWI, he trained tank corps in Pennsylvania as a lieutenant colonel in the Army. He is more famously remembered for serving as a five-star general and the Supreme Commander of the Allied forces in the European theater during WWII.