In every game of solitaire there are many known knowns, but it is a version that perhaps stresses the known unknowns that a certain former secretary of defense is turning into a videogame.

Now 83 years old, Donald Rumsfeld, veteran of three Republican administrations and the pharmaceutical industry, is revealing a new trick as an app developer, bringing a game he learned four decades ago in Brussels to iPads and iPhones around the world.

On Thursday, Mr. Rumsfeld and a company he works with released a videogame modeled on the card game British Prime Minister Winston Churchill played throughout World War II, as the story goes, to improve his strategic thinking.

Mr. Rumsfeld plays his cards close to his chest when it comes to crediting, or blaming, the game for his own wartime decision making. But he does say it hones strategic thinking and relaxes the mind when one is wrestling with a difficult problem.

“There is no question,” Mr. Rumsfeld said, “it is a game that requires you to be strategic, to look around corners, to think ahead, and to never give in—which is the phrase Churchill would have used.”