III.    Pins & Skewers.

Pins & skewers, along with forks, form what I call the “nasty triangle” of tactics and strategy. They all have at their center the goal of attacking and capturing pieces and pawns in very unpalatable situations for the opposing player.

Pin: is used to refer to the situation where a more valuable opposing piece is located behind another opposing piece or pawn which is being attacked by a player’s piece such that if the opposing piece or pawn is moved, the more valuable one behind is subject to being captured. “The piece which does the attacking is the pinning piece. The piece which is immediately attacked is the pinned piece. The piece which is shielded from attack is the screened piece.” [source: How Do You Play Chess? by Fred Reinfeld (pamphlet, Dover Publications, 1958, reissue 1972), at p. 20] A pin can never occur on an opposing King because the King is the most valuable piece in the player’s chess set, but a skewer may.

Skewer: is used to refer to the situation where a less valuable opposing piece or pawn is located behind another opposing piece which is being attacked by a player’s piece such that if the opposing piece is moved, the less valuable fighting unit behind is subject to being captured. A particularly strong skewer is where the more valuable piece in front is the opposing King in check, with only an option to move (check cannot be blocked and the checking piece cannot be captured either by the opposing King or any other opposing piece or pawn), and forced to move to a square where it cannot defend the less valuable opposing piece or pawn behind the opposing King from being captured.

• Any piece (except the King) may pin an opposing piece other than the opposing King, or an opposing pawn.
• A pawn cannot pin any opposing piece or any opposing pawn.
• Any piece (except the King) may skewer an opposing piece including the opposing King, but cannot skewer an opposing pawn.
• A pawn cannot skewer any opposing piece or any opposing pawn.
• A pin and a skewer are two variations on the same general principle – a player’s piece is attacking a forward opposing piece or pawn, which if moved will subject another opposing piece or pawn behind it to capture, or in the case of a pin involving the opposing King, then subject it to check.

There are two types of pins (skewers are skewers, no distinction like for pins):

1.    Absolute Pin.    This pin only occurs when a player’s piece or pawn is prohibited from moving or advancing because doing so would expose its King to check, the player does not have another piece to move or a pawn to advance and interpose between the King and the pinned piece, and the piece which is doing the pinning cannot be captured on the player’s next move.

2.    Relative Pin.    All other pins are relative pins because depending on the nature of the pin the player:

a.    may move the King or other piece or pawn behind the pinned piece to an available space safely out of the threat of check or being captured from the pinning piece and protecting the pinned piece or pawn; or

b.    has another piece to move or pawn to advance to a square interposing it between the King and the pinned piece or a pawn; or

c.    the player could choose to move the pinned piece or advance the pinned pawn and offer up his or her other piece or pawn behind the pin to the risk of being captured by the opposing player – for strategic, tactical, and/or positional reasons, thereby leaving the opposing player to ponder whether to capture the player’s piece or pawn (usually, but not always, a good thing to do).

Below are four diagrams showing examples of an absolute pin (Black’s Rook at d7 is pinned by White’s Bishop at b5), a relative pin (Black’s pawn at b7 is pinned by Black’s Bishop at e4), a skewer (Black’s Queen at d7 is skewered by White’s Bishop at h7); and an example of a pin being used in combination with a Queen sacrifice to force a Queen trade, accomplishing the goals of breaking an opposing significant pin on the player’s major piece, regaining material advantage, taking positional superiority away from the opposing player, and turning the game into a own game. In the relative pin diagram, Black’s Knight at f5 is not skewered because Black’s pawn at g6 behind is adequately defended by Black’s pawn at h7 and Black could also move his or her Knight from f5 to e7 thereby also protecting Black’s pawn at g6. In the skewer, although Black could move his or her Knight at f6 to g4 (Ng6) to interpose it between White’s Bishop and Black’s Queen, White would simply capture Black’s Knight with White’s Bishop (Bxg6) again skewering Black’s Queen. Explanation of the pin combination follows the diagrams.

The pin combination diagram is from Schallop-Paulsen 1880. White’s Bishop is pinning Black’s Knight at f7, Black has material advantage 27 to 23, and (at least face value) positional superiority because White’s King is trapped into the two squares at h2 and h3 because of Black’s Rook at g8 while White’s Rook also is pinned at h3 by Black’s Queen at h6. With White to move, White proceeds to sacrifice his or her Queen by capturing Black’s Rook at g1 checking Black’s King at h1 (Qxg1+!!) forcing Black to capture White’s Queen with Black’s King (Kxg1, the only move available for Black), and thereupon White captures Black’s Queen with White’s pinned Rook at h6 (Rxh6). Black cannot capture White’s Rook at h6 with Black’s Knight because of White’s pin on the Knight with White’s King Bishop at d5.

Thus, White breaks pin on the White Rook and captures an opposing Rook and a Queen (14 points) for a Queen (9 points) for a gain of 5 points in material count via the forced Queen trade by White’s Queen sacrifice. Black’s King is flushed into the compromised position in the open g file at g8, with Black’s Knight being pinned and Black’s Rook being ineffective to provide any attacking or defense power for Black’s King.

Black’s Rook cannot move to c6 because White’s King Bishop at d5 would capture it (Bxc6) and if this line is followed, Black’s pawn at b7 could capture White’s King Bishop (bxc6) and White’s Rook would capture Black’s pawn (Rxc6) gaining another point in material for White and removing Black’s remaining major piece and a pawn (6 points) from the board in exchange for just a Bishop (3 points), a further gain of 3 points in material count, although this would free Black’s Knight from the pin.

Black’s Rook cannot move to the b file because it is blocked by Black’s pawn at b7, and would be highly unwise to move to d7 because White would simply move White’s Knight to f6 thereby fork checking Black’s King with capture of Black’s Rook to follow (Nf6+ K moves, Nxd7).

White has several options to pursue. Generally, the best course when up in material? Start exchanging and trading away pieces, with an eye toward Queening (gaining back a Queen) via pawn promotion…notice White’s remote isolated pawn (a player’s pawn in a file not connected with any of the player’s other pawns able to defend it and a significant distance – remote – from the opposing King), which is located at a2. Some possibilities are:

If Black moves Black’s King to g7 (Kg7) to threaten White’s Rook at h6 and thereby freeing Black’s Knight from the pin, White captures Black’s Knight at f7 with White’s King Bishop at d5. This creates two unpalatable situations for Black.

If Black captures White’s King Bishop with Black’s King (Kxf7), White moves White’s Rook and captures Black’s pawn at h7 skewering and checking Black’s King (Rxh7+), and after Black moves the King to an available square in the 6th or 8th ranks, White captures Black’s Rook at c7 (Rxc7).

If Black captures White’s King Bishop with Black’s Rook (Rxf7), White moves White’s Knight to g5 attacking Black’s Rook at f7. Black would be obliged to move the Rook to try to save it. If Black moved it to e7, White moves White’s Rook and captures Black’s pawn at f7 skewering and checking Black’s King. Black must move Black’s King to either the 6th rank or 8th rank, opening Black’s Rook to capture by White’s Rook. There are only four squares Black’s King would be able to move to: f6, g6, f8 , & g8. If Black’s King moved to g8, Black would have a free capture of Black’s Rook (Rxe7). If Black’s King moved to g6 (Kg6), White would capture Black’s Rook (Rxe7) and Black would be able to capture White’s Knight (Kxg5), but this also is not good for Black [losing 5 points (Rook) to only 3 points (Knight)] with the King now flushed into an open board position. If Black’s King moved to f6 (Kf6) to attempt to defend the Rook with the King and also threaten White’s Knight at g5, White captures Black’s Rook with White’s Rook forcing Black to capture White’s Rook in a Rook trade giving White the King, a minor piece (Knight), and 3 pawns, against Black having only the King and four pawns. If Black moved Black’s King to f8 (Kf8) to defend Black’s Rook, then White could capture Black’s Rook (Rxe7) forcing Black to capture White’s Rook with Black’s King (Kxe7) in a forced Rook trade, giving White the King, a minor piece (Knight), and 3 pawns, against Black having only the King and four pawns.

After the forced Queen trade, Black’s poorly defended Knight at f7 and pawn at h7, as well as Black’s Rook, are all prime targets for attack and capture by White using combinations because White has three pieces…Rook, Bishop, & Knight, and Black cannot adequately defend either against a combined attack by the three pieces. Obviously, White has turned the game into a won game, and Black likely (and should) simply resign. A nice example of the simple elegant power of combinations working hand in hand to crush an opponent.

Now let’s turn to the basic principles and rules applicable for moving the pieces and advancing the pawns along with further development of tactical and strategic concepts. Links also provided to view/download/print this lesson in pdf format, to individual tutorials on each piece and the pawns, and to the next tutorial, the main chess page, and my web home.