Allan Calhamer, a Harvard-educated postman who invented Diplomacy, which for more than half a century has been a favorite board game of calculating, caffeinated intellectuals, died on Feb. 25 in La Grange, Ill. He was 81.

The cause was heart and kidney failure, his family said.

Mr. Calhamer (pronounced CAL-uh-mur) conceived Diplomacy at Harvard in the mid-1950s, and from the start its object was simple: to achieve world domination in as many hours (or days, or even years) as it takes.

Released commercially in 1959, Diplomacy has sold more than 300,000 copies. It was reported to have been a favorite game of Henry Kissinger; John F. Kennedy and Walter Cronkite were also said to enjoy it. In 1984 it was named to Games magazine’s Hall of Fame, alongside stalwarts like Monopoly, Clue and Scrabble.

Over the years, Diplomacy — “Dip” to its most fervent adherents — has inspired a welter of fanzines, international tournaments and, most recently, online competitions.