How to Win at Fortress

Fortress is a traditional solitaire, one of the oldest open solitaires (games where all of the cards are dealt only once, face up, at the start), and at one time one of the most popular: Alphonse Moyse Jr., in 150 Ways To Play Solitaire (1950), calls Fortress "perhaps the most popular of those in which the whole pack is laid out." It dates back at least as far as Lady Adelaide Cadogan's Illustrated Games of Patience, the first English-language book on solitaire, which was published in the 1870's. Originally a French game (La Forteresse), it is one of only four one-deck games in Lady Cadogan's original book. The deck is dealt out into ten rows of five cards each, the two extra cards going on the first two rows. The four foundation piles are built up in suit from ace to king; the ten tableau rows can be packed in suit either up or down. That is, if the seven and eight of clubs are both uncovered, either card may be placed on the other. An uncovered card from any of the other rows may be placed in an empty row -- this is an important point missed by some computer implementations, which only allow kings to be placed in an empty row (making the game essentially unplayable). Only one card at a time can be moved; we'll see how this works later. Some packages make the game too easy by allowing the tableau to be packed regardless of suit (as in Beleaguered Castle, a later offshoot of Fortress) and allowing any rank to be selected as the starting rank for the foundations (as in the variant Chessboard). There is nothing wrong with these games, but Fortress provides a very challenging game when played by the traditional rules. The game is correctly programmed in several of the better packages, including BVS Solitaire, Pretty Good Solitaire and Solitude for Windows.

Fortress 1

The Solitaire Virtuoso program now has a working version of Fortress with a nice added feature: sequences automatically reverse when they are either selected and moved onto another card, or right-clicked and sent to an empty column. Above is an example deal, number 59492 from the new Solitaire Virtuoso program. Here the tableau is simply dealt in ten columns. There are no aces uncovered at the start; if any become uncovered, they will automatically move to the foundations, along with any succeeding cards in suit (since this is a single-deck game with packing in suit, there is never a disadvantage to playing every possible card to the foundations, though Autoplay can be turned off if desired). The program also keeps a written solution (the display of this can be turned on or off at will), using a simplified version of standard FreeCell notation: every move is recorded as two numbers, showing the starting and ending column of each move (using A to indicate column 10). Cards which go to the foundations automatically are not recorded in the solution.

Having aces available at the start is not necessarily that valuable; what we want is lots of cards of adjacent ranks in the same suit, which can be played on each other. If we cannot clear at least one row fairly quickly, there is no hope of a win. We see here that there are two hearts of adjacent ranks (78) and two spades (89). This is not usually too promising, but if we look carefully at column 2, there are lots of cards adjacent in rank and suit to cards which are already uncovered, or which can be uncovered quickly. In fact, we can clear the whole column with a quick set of moves. Put the seven of hearts on the eight, the seven of diamonds on the eight, the jack of clubs on the ten, the nine of hearts on the ten, and the six of clubs on the seven. Now put the eight of spades from column 6 on the nine, uncovering the ace of clubs (which goes to the foundation), the newly exposed six of diamonds on the seven, and the five of diamonds on the six. Now we have an empty column, a promising start (though many games are still lost even after clearing a whole column). We have turned on the solution display in the screenshot below. If we can clear a second column, the chances of winning become much higher.

Fortress 2

Since only one card at a time can be moved, we can't take the seven-eight of hearts as a group and simply place it directly onto the nine-ten. But since we now have an empty column, we can move it there via reversal, which is a hallmark of Fortress. Right-click on the seven or eight of hearts (actually anywhere in column 4, since the program knows which cards can move), and the seven of hearts moves to the empty column 2, followed automatically by the eight. [There are actually two ways of moving a card or sequence to an empty column: either right-click, which sends all available cards in reverse order to the first empty column, or simply click to select, and click on the empty column where you want the card(s) to go.] Now click normally (i.e. left-click) on either the seven of eight of hearts (selecting and highlighting both), and click on the nine of hearts to move them both there in correct sequence. Now if we move the queen of spades to column 2, which is empty again, the ace of diamonds will go to the foundation, we can play the five of clubs onto the six, and the two of clubs goes to the foundation. We've traded one empty column for another, but made some progress.

We want to clear a second column, but there doesn't seem any obvious way to do so, nor are there any obvious free moves which will make progress without using up our empty column. Column 8 looks promising, but if we simply reverse the five-six-seven of clubs into the empty column and play the five of hearts onto the four, we will be stuck, since the four of clubs won't play onto the seven. However, a clever maneuver will enable us to clear column eight. After reversing the five-six-seven of clubs into the empty column 4, move the four of hearts onto the five! This frees the jack of spades, and we can put the queen of spades there to regain an empty column. Now reverse the seven-six-five of clubs into the empty second column (see below).

Fortress 3

Now the four of clubs has somewhere to go, and reversing the four-five of hearts allows column 8 to clear (four of clubs on five, four of diamonds on five, ace of spades to foundation).  If we can get the ace of hearts to the foundation, we can clear all of column 1 (since we can see that the twos would go to the foundation and the remaining cards have places to go).  But we still only have one empty column, and we need to get the ten of spades uncovered.  Reverse the queen-jack of spades, play the queen of diamonds on the king, and the ten of spades on the jack.   Now we can reverse the eight-nine of spades and then put them on the ten.  Now the ace of hearts goes to the foundation, and we reverse the five-through-eight of diamonds.   The twos (and three of spades from column 3) autoplay, then the jack of diamonds goes onto the queen, the queen of clubs onto the jack, and the ten of diamonds on the jack.

Fortress 4

Now the road to victory is open, as we can empty two more columns quickly.   Put the nine of diamonds, followed by the ten-through-king, onto the eight.  Put the five of spades on the six, and the six of hearts (followed by the five-four) on the seven.  We plan to clear column 9 next, so reverse the eight-through-queen of spades so that there is somewhere to put the king (this isn't strictly necessary, but it is good technique not to waste columns).   Now reverse the queen-jack-ten of clubs (four-five-six of spades autoplay), and put the king of spades on the queen.  This autoplays the threes of clubs and hearts, followed by the four-through-ten of hearts and the four-through-eight of clubs.  Now reverse the eight-through-king of spades (which autoplay immediately) and the king-through-four of diamonds.  Now play the queen of clubs to an empty column (strangely, this is the first time we have touched column 10), and everything else autoplays.

The full sequence of moves is:

 24 21 29 25 28 63 61 21 42 25
 42 48 84 78 27 42 84 82 81 78
 67 68 36 68 16 17 19 17 36 76
 73 75 45 81 94 91 12 61 A2

Undoubtedly Fortress is a difficult game: the win rate is somewhere between 10% and 15% (one package gives a ridiculous estimate of 1 in 100), but the game is a very satisfying one to win. In some ways Fortress is an ideal solitaire for the computer; when you get an unwinnable deal, you can just go on to the next one. To my knowledge no one has programmed a Fortress solver; combining such a solver with a playing program would allow it to generate only winnable deals by request.

This article is copyright 2008, 2009, 2011 by Michael Keller. All rights reserved. Most recently edited on July 3, 2011.