Now a few thoughts on the strategic implications of our work on pawn forks.
An easy way to get nailed by a pawn fork is to allow one of your pieces to get trapped on a square where it has limited motion. Bishops and knights near the side of the board are especially vulnerable to this type of trouble; a knight has a maximum of eight flight squares when it is well-placed, but when it’s on the side of the board it may have only four or even fewer, and then it is easy for some of those squares to be occupied by its fellow pieces or to be under attack by the enemy. Likewise, a bishop in the middle of the board may be able to move in four different directions; but a bishop on, say, a5 with one of its own pawns behind it on b6 can only go one way, and has a maximum of four escape squares. There are lots of ways for pieces stuck in this way to be taken by pawns, either directly (they simply get trapped) or by being threatened in ways that force them to move onto squares where they get forked.
There is additional reason to worry whenever you see pieces being used as defenders of other pieces—or of pawns. For then if the man under attack gets taken, it is replaced by a new valuable target that may be loose or underdefended. When you do protect your men with other pieces, remember that as soon as the protectorate gets taken, you will be forced to move the guarding piece onto a square of your opponent’s choosing. There it may become a target. It may be loose; it may lack the defensive powers of the piece it replaced; it may have greater value than the piece it replaced. Thus we saw a number of examples in this chapter of exchanges where pawns were taken and pieces performed recaptures—and then the pieces got forked. Lesson: when you press a piece into service protecting a pawn, give thought to the danger that it can be drawn onto the pawn’s square with a capture.
Since pawn forks often are the residue of exchanges initiated by pieces (a bishop takes a piece and gets recaptured; then comes the pawn fork), it follows that you can expect better success with pawn forks when you have a well-mobilized army—pieces on open lines attacking lots of enemy squares and putting pressure on enemy pieces. Those are the positions that give rise to exchanges that make pawn forks and other double attacks possible.
Notice generally, too, that victims of pawn forks often do not have good control of the center of the board. For a pawn to fork two pieces it often has to pass through the center or be operating in a sector where it is more advanced than the pawns on the other side (otherwise the enemy pawns interfere with its attacking movements). Pawns established in the center are most likely to be in a strong position to make or threaten forks because it is easy for enemy pieces to gather on the same rank in their own territory where enemy pawns in the center can reach them.