Former US Secretary of Defense Donald Rumsfeld has a new business venture.

Rumsfeld has launched a phone and tablet app called "Churchill Solitaire," a variation of the classic single-player card game.

The game is a variation of Solitaire credited to former British Prime Minister Winston Churchill.

Rumsfeld, who served twice as Secretary of Defense from 1975-1977 and from 2001-2006, says that Churchill taught a friend to play, and that friend in turn taught Rumsfeld. The game uses two decks of cards instead of one and involves 10 rows of cards instead of seven.

The app is free, but in-app purchases are available. Rumsfeld says profits from the game will go to military charities.

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