He was an inveterate poker player
Truman was a poker player long before entering the White House and he enjoyed the game so much that as President he had a set of chips made embossed with the Presidential Seal. The famous phrase associated with Truman – The Buck Stops Here – was a reference to poker, derived from the use of a buckhorn knife being used to designate the button, for the position of the dealer. Truman by most admissions played the game well and preferred to play stud poker, with no wild cards.
Winston Churchill enjoyed poker too, although by most admissions he did not play particularly well, and his fondness for brandy helped his play deteriorate as a game went on. In one game played in the President’s private rail car, the Ferdinand Magellan, both Churchill and Truman played, with several other notables and members of the press alternating in the other seats.
While Churchill was on a break from the game, Truman warned his fellow players to allow the statesman to start winning. Whether it was out of sympathy or the President had diplomatic reasons for instructing the others to go easy on Churchill has never been revealed; Truman said no more about the matter.
After leaving the presidency Truman continued to enjoy the game, playing in a weekly poker group comprised of local businessmen (mostly Republicans) in the 822 Club in Kansas City, Missouri. Truman tried to avoid being photographed while playing during his presidency, a whim he discarded during his retirement. (Note: In the photo above he is watching, not playing) His successor, Dwight Eisenhower, decided that poker presented a poor image for a world leader, and frequently played contract bridge instead.