There is a moment, the first time you deal Forty Thieves, when the board simply looks wrong. Ten columns, four cards each, forty cards face up in a wall - and eight foundations to fill instead of four. Everything about it says this should be easier. There is more information, more space, more of everything.

It is one of the hardest patience games ever put in front of a player, and understanding why is the fastest way to understand what actually makes a solitaire game difficult.

More cards is not more freedom

The instinct is that a second deck doubles your options. It does not. It doubles the work while leaving the working space almost unchanged.

In Forty Thieves you must build foundations up from ace to king in suit - eight times over, because there are two of every suit. That is 104 cards that each have to arrive in a specific order. Meanwhile the tableau gives you ten columns, builds down in suit, and lets you move exactly one card at a time.

That last restriction is the whole game. No moving ordered runs as a unit. If you want to relocate five cards, you need somewhere to put four of them first, one at a time. An empty column is therefore not a convenience - it is the only real resource in the game, and it is worth roughly what a free cell is worth in a one-deck game.

The arithmetic that makes it brutal

Work through the consequences and the difficulty stops being mysterious:

  • Same-suit building halves your legal moves. A red six takes a red five in Klondike terms; in Forty Thieves it must be the same suit, so roughly one in four cards will fit where one in two would have.
  • Duplicates block each other. Two identical cards are not two chances - they are two cards that both need the same slot, and one of them is very often buried beneath the other's path.
  • One-card moves make depth expensive. Digging a card out from under four others costs four separate placements, each of which needs a legal home.
  • The stock deals once. No redeal. Every card that goes to the waste and does not come off again is gone.

Put together, the win rate for a competent player is low enough that many implementations quietly offer easier relatives instead. That is not a flaw. It is the design.

Why the difficulty is honest

Here is the thing that makes Forty Thieves worth playing rather than just surviving: almost nothing is hidden. The tableau is dealt face up. You can see the wall you are up against from move one.

Which means the game is not doing to you what Klondike sometimes does. A Klondike loss can be a dead deal - face-down cards in an order no amount of skill unpicks. A Forty Thieves loss is usually a sequencing failure you could, in principle, have avoided.

That places it right next to the other great open-information patience game. In FreeCell, everything is visible too, and the near-total solvability of its deals makes every loss a solving error. Forty Thieves is the same contract with a far crueller ratio: fewer deals are winnable, but the ones that are, are winnable by thinking.

Compare that with the classic Klondike form on the main board - the face-down cards there are genuinely unknowable, and a share of deals are lost before you touch them.

How to actually win one

Five habits, in rough order of importance:

  • Treat empty columns as currency. Do not fill one because you can. An empty column is a four- or five-card manoeuvre you have not spent yet, and filling it with a random king is usually the losing move.
  • Do not rush the foundations. A low card sent up early is a card that can no longer catch a card below it in the tableau. In a two-deck game that mistake compounds, because its duplicate needs the same help later.
  • Work the waste pile before it sets. The stock deals once. Anything you plan to use from it has to be caught on the way past.
  • Break up long same-suit runs early, while you still have the space to do it one card at a time.
  • Count the cost before starting a dig. "Four cards deep" means four legal homes, and if you cannot name all four, do not start.

That last one is the general skill. It is planning a sequence rather than taking the move in front of you, and it is the thing almost every good game teaches somewhere. Anyone who has learned not to create a dependency they cannot resolve when they play Tetris online is doing the same arithmetic under time pressure, and anyone who clears a crowded board when they play Mahjong online is choosing which of four identical tiles to spend for the same reason.

The gentler two-deck games

If Forty Thieves is too much, the family has softer members that keep the two-deck arithmetic and relax one constraint each. Some allow alternating colours instead of same suit. Some allow moving sequences as a unit. Some grant a redeal. Each of those changes the game more than it sounds like it should, which is itself a useful lesson in how tightly wound the original is.

On this site, Spider is the other two-deck game, and it is instructive precisely because it solves the same problem differently: it keeps the two decks but gives you the ability to move ordered runs, and hides information instead. Two decks, two philosophies.

Give it a go

Deal a few hands of Forty Thieves with no intention of winning, just to feel where it locks up - most players find the same wall in the same place, around the point where the third column needs dismantling and there is nowhere to put anything. Then read the rules hub for the exact move legality, and try the daily deal, where everyone gets the identical shuffle and a win is genuinely comparable.

And if the one-card-at-a-time restriction is what you want to escape rather than master, the games that abolish it entirely are Yukon and Scorpion.