US Presidents Trivia: Who is the only President to serve in the army after the conclusion of his Presidency?

Having military experience isn't a prerequisite to becoming President of the United States, but is sure does help win a campaign.  31 of the 43 men to serve as President had some form of military experience, with 12 achieving the rank of general.  The President is the Commander and Chief of the United States and is actually a civilian; as a result, military service ends with (or before) ascension to the Presidency.  However, once in US History, and only once, has a President rejoined the military after serving as President.  So, off of Pocket Trivia: US Presidents - Who is the only President to serve in the army after the conclusion of his Presidency?  Was it:

• George Washington
• Dwight Eisenhower
• Andrew Jackson
• Ulysses Grant

All four of the men above were Generals in the United States Army before becoming President - but the correct answer is Washington.  In 1798, after Washington had left office, it appeared that war with France would occur.  Washington was asked to rejoin the army to lead it, a responsibility which he accepted.  Washington participated in planning for a possible war, but never lead troops into battle (as the war never actually came).