Which of the following U.S. Presidents was NOT a former general?

The correct answer is John F. Kennedy, as he was the only one among the given choices who did not hold the rank of general in the military. While Eisenhower was a five-star general in the Army during World War II and played a crucial role in planning the D-Day invasion, Andrew Johnson served as a military governor during the Civil War but did not hold a general's rank. Franklin Pierce, although not as prominently recognized as a military leader, also served as a general in the Mexican-American War. In contrast, Kennedy served in the Navy during World War II but ultimately did not rise to the rank of general, highlighting his distinction from the others in this context.