Forty Thieves Solitaire

How to Play Forty Thieves

Forty Thieves is a long two-deck game with famously strict rules: columns build only in suit, only one card moves at a time, and you see each stock card once.

It rewards patience and planning. A won game of Forty Thieves is a real achievement.

Setup

Two decks are shuffled together. Forty cards are dealt face up into ten columns of four, giving the game its name. The other 64 form the stock, and eight foundations wait above.

Rules

• Foundations build up in suit from Ace to King. There are eight, two for each suit.
• Columns build down in the same suit.
• Only the bottom card of a column can move, and only one card at a time.
• Any single card can move to an empty column.
• Click the stock to turn one card onto the waste. The top waste card can be played.
• You get one pass through the stock. There is no turning it over.

How to win

Move all 104 cards to the foundations, in eight piles from Ace to King.

How often can Forty Thieves be won?

We ran our own solver on 200 shuffled deals of this version. It found a win in 5 of 200 (3%), and ran out of its budget of 200,000 positions a deal on 195.

Those undecided deals may still be winnable, so treat the win count as a minimum. The solver can see every card, including face-down ones, so it measures what the cards allow, not how often a person will win.

Forty Thieves Strategy

• Emptying a column is the big goal. With one-card moves, an empty column is how you take apart a pile to reach something underneath.
• Don't turn a stock card without checking the board first. If you can make a useful move now, make it, because the waste card you cover may be gone for good.
• Keep the waste in mind as a stack. Cards on it come back in reverse order, so burying something there means playing everything on top of it first.
• Aces are worth digging for, but don't tear down good in-suit sequences only to reach them.
• Long in-suit sequences are hard to shift one card at a time, so build them where they won't cover cards you still need.

History

Recorded as early as 1870 as Napoleon at St Helena, and also known as Big Forty and Roosevelt at San Juan. The name Forty Thieves appears in American sources from the 1920s.

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Forty Thieves FAQ