Lesson 9 - Basic Chess Tactics: The Pin

The pin is the most common tactic in chess. We can find it in all phases of the game. This tactic happens when an attacked piece is immobilized (pinned) because if it moves, it will discover an attack upon another piece of greater value behind. If the piece behin the pinned piece is the king, we qualify the pin as being "absolute" and if it is another piece than the king, the pin is qualified as being "relative". Also, only long range pieces (queens, rooks and bishops) can pin other pieces. Let's see together more details and some examples.

The absolute pin is more efficient than the relative pin since it involves the king. Indeed, the pinned piece cannot move as it would reveal a check to the king which is illegal (a player is forbidden to do a move that puts his own king in check). Here is an example of an absolute pin occuring after the opening moves 1.e4 e5 2. Nf3 Nc6 3. Nc3 d6 4. Bb5 :

Diagram 9.17 - Absolute pin on the c6 knight by the b5 bishop

As we can see, the last move played by White brings the f1 bishop to b5 in order to attack the c6 knight. Despite the fact the the knight is protected by the b7 pawn, Black can no longer count on this knight as it is immobilized because if the knight moves, the b5 bishop will check the black king whhich is occupying the same diagonal than the knight and the bishop. The pin is not really a threat for the moment as the knight and the bisop are worth the same value. We can say that the bishop is winning its fight over the knight for now, but Black is not required to take care of the pin immediately. He must stay alert however and keep in mind that the knight is immobilized when working on his plans.

Let's now see a more striking example: a pin done on a piece of greater value.  In the below diagram, Black has just captured a piece that was sitting in front of his king with his queen... he did certainly not think about the following possibility for White: Re1! which is pinning the queen! Since it is an absolute pin, the black queen cannot escape from this threat and black is forced to exchange the queen for the rook. White will have the upper hand in the exchange. Note that if White plays 1. Qe1 or 1. Qe2, the black queen would still be pinned but the pin would not be efficient as Black would then be able to exchange the queens and White would not gain any material advantage out of this pin.

Click here to see the move Re1.	Diagram 9.18 - Absolute pin against the black queen

The relative pin involves another piece than the king. This means that the pinned piece is allowed to move since it will not constitute an illegal move. We can find relative pins in several opening lines. Here is one we can obtain after the following moves: 1. e4 c6 2. Nc3 d5 3. Nf3 Bg4:

Diagram 9.19 - Relative pin on the f3 knight by the g4 bishop

The g4 bishop pins the f3 knight since if the knight moves, Black would quickly jump on the white queen with the move Bxd1.  We say that the pin is relative since white can decide to move the knight anyway as it is not an illegal move.

Since a piece is allowed to move when being in a relative pin, we need to stay alert about the possibilities available to the pinned piece as it can do a surprising move when we least expect it. Let's observe this last statement in the following example. The position is reached after the moves 1.e4 e5 2. Nf3 d6 3. Bc4 g6 4. Nc3 Bg4. In this position, we note that the g4 bishop is pinning the f3 knight on the white queen. However, this pin is not efficient since White can play:

This example nicely demonstrates that we have to be careful when dealing with a relative pin. As it is the case with the fork, the victim of a relative pin might have the possibility of playing an in-between move to eradicate the pin's effect. Indeed, as we can see in the following example, White uses an intermediate check to unpin a piece. In the diagram below, the b5 bishop is pinning the c4 knight on the f1 rook.  In order to break the action of the pin, White plays 1... Nxd6+.

Click here to see the move Nxd6+.	Diagram 9.21 - Unpinning a piece with an intermediate check

Black is required to stop the check by moving his king on his next move, giving the chance to White to capture the bishop or move his rook on a safe square (on c1 for example...) to prevent being captured by the b5 bishop.