Forty Thieves Solitaire Strategy Guide
Forty Thieves is one of the hardest solitaire games. Two decks, ten columns of four face-up cards, one card moved at a time, and a stock you turn over only once. Almost everything is visible from the first move, so it rewards patience and planning far more than speed. This guide covers the opening, how to build without burying cards, how to make and use empty columns and how to spend the stock.
Opening principles
You start with 40 cards face up in ten columns, eight empty foundations and a 64-card stock. Only the bottom card of a column can move, so before you touch anything, read the whole table.
- Locate every Ace. Aces buried deep in a column decide how long the game can last. Note which columns hide them and how many cards are on top.
- Look for cards that fit. A card moves onto the next-higher card of its own suit, so scan the bottom cards for pairs like a 6 and a 7 of the same suit.
- Make the free moves first. Any Ace that is already at the bottom goes to a foundation straight away; it is never wrong.
Building without burying
Because you can only move one card at a time, the order of cards inside a column matters more than anything else.
- Check what a move covers. Putting a card on a column buries the card beneath it. If that card is one you need soon, find another place for the card you are moving.
- Avoid covering low cards with high ones. The 2s and 3s are what the foundations need next, so keep them near the bottom of their columns.
- Remember the duplicates. There are two copies of every card. If one copy is blocked, the other may be free, so you can often choose which King, Queen or Jack to build on.
Empty columns
An empty column is the most powerful resource in Forty Thieves. It can hold any single card, so it works like a free cell that you can also build on.
- Empty a short column early. A column of one or two cards is the cheapest to clear; look for a place for each of those cards before you do anything else.
- Do not fill the space with a card you cannot move again. A card put into an empty column should either have a place to go later or start a useful same-suit sequence.
- Moving the only card of a column into an empty column achieves nothing. It just swaps one empty column for another.
Using the stock
The stock has 64 cards and is turned over exactly once, so each card is a one-time chance. The top waste card is the only waste card you can play.
- Do all your useful column moves first. Only then turn the next stock card. Turning early burns cards that you could have placed more usefully later.
- Think before you turn. If a turned card does not fit anywhere, it stays on the waste, and the next card you turn covers it.
- Use the waste to make space. Sometimes the right way to use a stock card is to put it on a column so that a card underneath is freed.
Common mistakes
- Moving on autopilot. Many moves look free but bury a low card. Before every move ask what it covers and what it uncovers.
- Filling empty columns too quickly. An empty column is worth much more while it stays empty.
- Turning stock cards when a column move is still available. Make the table work first.
- Rushing every card to the foundations. Aces and twos go up at once, but a middle card is sometimes more useful in a column as a base for a lower card.
- Playing on after the deal is dead. If every card you need is buried under cards that cannot move and the stock is nearly gone, start a new deal.
How winnable are the deals?
In the standard game only about 10% of deals are won, and many random deals cannot be won at all. In our screening, the solver found a full winning line within its search limit for about 9% of 12,000 random deals (1,095 of them). That figure is a lower bound, because a solver with a limited search can miss lines. New games and the Daily Challenge only use deals the solver has proved winnable, so a winning line always exists. Because few deals qualify, the library is small and you may see the same deal more than once. The solver sees the whole stock, and you do not, so winnable does not mean easy.
Practice and play
Play a few deals with one habit: before every move, say which card it uncovers and which card it covers. That habit is worth more than any single trick in a game where you can move only one card at a time.