### Instruction: How many U.S. Presidents have served in the military?
### Response: Twenty-six U.S. Presidents have served in various branches of the military.
George Washington
Thomas Jefferson
James Madison
James Monroe
Andrew Jackson
William Henry Harrison
John Tyler
James K. Polk
Zachary Taylor
Millard Fillmore
Franklin Pierce
James Buchanan
Abraham Lincoln
Andrew Johnson
Ulysses S. Grant
Rutherford B. Hayes
James A. Garfield
Chester A. Arthur
Benjamin Harrison
William McKinley
Theodore Roosevelt
Harry S. Truman
Dwight D. Eisenhower
John F. Kennedy
Lyndon B. Johnson
Richard M. Nixon
Gerald R. Ford, Jr.
Jimmy Carter
Ronald Reagan
George Bush
George W. Bush