A fork, also known as a double attack, occurs when a single piece attacks two or more enemy pieces at the same time. This is one of the most effective ways to win material, because it is often difficult to save all the pieces that are attacked before they can be taken. All the pieces - even the king - are able to perform a fork, but the real master of the fork is the knight.
The knight's often surprising ability to jump into unexpected places, combined with its ability to attack in eight directions (the bishop and rook can attack in only four), make knight forks a constant threat throughout the chess game. Here are some common examples:
Compared to knight forks, pawn forks are easy to spot. The pawn can only attack the two squares diagonally in front of it, so to spot a potential pawn fork, you only need to see where two pieces stand on the same rank with a square between them. Here's a simple example.
Still, there are times when a pawn fork can be unexpected. Take a look at this example, which frequently occurs in beginner and novice games.
As the most powerful piece, you'd expect the queen to be a dangerous exponent of the fork. The queen is dangerous as long as she is on the board, but in the opening when the enemy king is still in the centre, possibilities for queen forks abound. Like knight forks, queen forks can be tricky to spot, although for different reasons. The reason queen forks can be unexpected is because she can attack pieces at opposite sides of the board. Here is an example:
Rook forks are most dangerous in the endgame, when there are few pieces left to protect all the pawns. Pawns become very important in the endgame, when both sides are trying to make a new queen, so winning a pawn with a rook fork can be decisive. Here is a typical example of how pawns can be vulnerable to rook forks in the endgame.
The bishop is not usually the best for performing a fork, but it does happen from time to time, and you still need to watch out for opportunities. Here is an example of one of the more common bishop forks, which can happen in the opening when the opponent's king hasn't yet castled.
The king is slow and vulnerable to check, but he can attack in eight different directions so he can still pull off a fork if the opponent's pieces are not protected. This usually happens in the endgame, because it isn't safe for the king to go chasing after enemy pieces while the opponent still has significant forces on the board.
A fork doesn't just have to attack pieces. You can fork squares as well. What does this mean? Take a look at the following example:
Now it's your turn to test what you've learned about forks. On each of the boards below, try to find a fork for the indicated side.
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