This article first appeared in the St. Louis Beacon, March 21, 2012 - Strategy is important in chess, but a chess game can be lost quickly when one makes a tactical oversight. It is important for all levels of chess players to understand tactical ideas, as most games are ultimately decided by blunders, errors or misunderstanding of tactics.
In chess terms, tactics usually refer to ideas such as forks, skewers, pins, X-rays and various types of checkmates.
A fork, when two or more pieces are attacked at once, is one of the most common tactical ideas. This can be quite precarious (for one of the players!) since it is impossible to move two attacked pieces at once. The most deadly fork is one that attacks the king and queen at the same time. This is called a "royal fork" and is typically executed by a knight. The royal fork usually results in an easy win for the fork-er after a swift resignation by the fork-ee.
A less common occurrence is the dreaded "family fork." This is always executed by a knight, and occurs when a king, queen and rook are simultaneously attacked. Forks normally occur when you have many pieces on the same color because the knight, bishop and pawn can only attack one color on any given move.
Skewers are another excellent way to win pieces. A skewer is an attack of a piece and also another piece directly behind it, either diagonally or on the same file or rank.
A pin is similar to a skewer, except a skewer occurs when you have the stronger piece in front of the weaker piece, and a pin is the opposite. If my bishop is attacking my opponent's knight, for instance, and his or her queen is on that same diagonal, then the knight is effectively pinned because moving it away means losing the queen.
An X-ray is similar to a skewer, but it usually refers to a defensive idea of protection rather than an attack designed to win material. I prefer X-ray defenses, whereupon your piece defends through the opponent's piece.
When I teach checkmate, the three main situations are back-rank checkmate, checkmate against the uncastled king, and checkmate against the castled king. Depending on the position of the pieces and how many of them are still left on the board, each of these types of checkmates can look very different. It is important to get accustomed to seeing the various patterns so you can both deliver checkmate and avoid being checkmated yourself!
These ideas are an important start to understanding the theory of tactics, but one must continue to study to create a deeper tactical understanding. At 7 p.m. on Thursday, March 22, I will give a lecture at the Chess Club and Scholastic Center called "Improving Your Tactical Eye." The lecture, which is free for members of the chess club, (and memberships are just $5 a month or $30 a year for students or $12 a month or $80 a year for adults) will delve deeper into some of the ideas introduced in this article and hopefully offer players a better tactical understanding and awareness.