Former Defense Secretary Donald Rumsfeld is stepping out of retirement for a stint as an iOS app developer.

The 83-year-old veteran of three Republican administrations has turned a decades-old game into a modern challenge.

Churchill Solitaire—as in Sir Winston—features two decks, a "Devil's Six" row of cards, and timed scoring, and will leave you pulling out your hair as you aim for victory.

"When I learned the game from [a NATO colleague], I found it to be one of the most entertaining and strategic card games I'd ever played," Rumsfeld said in a statement.

Begin your journey as a cadet at the Royal Military Academy Sandhurst, just as 18-year-old Churchill did in the late 1890s. You can try and retry three free deals—easy, medium, hard—or upgrade to premium to gain access to even more options.

The objective is deceptively simple: Move all 104 cards to the Victory Rows at the top right of the screen; start by dragging or double-tapping Aces. But this isn't just another lonely game of solitaire: One key difference is the Devil's Six.

Dealt at the beginning of each hand into a line at the top of the screen, these cards can only be moved directly to the Victory Rows, never to the main playing board. Liberate the Devil's Six to win.

Like regular solitaire, players must create columns of cards of opposing colors in descending order. Get stuck? Ask for a hint, or replay the entire hand. Earn promotions and achievements to work your way toward becoming Prime Minister.

Connect to the iOS Game Center to challenge friends via Facebook, Twitter, or email. Churchill Solitaire is currently available only for iOS; an Android version is expected in the coming months.

"I suppose there are not many people at my advanced age involved in mobile apps," admitted Rumsfeld, a self-confessed technology novice. "But I've found Churchill Solitaire keeps a mind sharp. And besides, I've enjoyed beating the young folks who have tried to keep up with my score."