Chess strategy

Chess strategy is the aspect of chess play concerned with evaluation of chess positions and setting goals and long-term plans for future play. While evaluating a position strategically, a player must take into account such factors as the relative value of the pieces on the board, pawn structure, king safety, position of pieces, and control of key squares and groups of squares (e.g. diagonals and open files). Chess strategy is distinguished from chess tactics, which is the aspect of play concerned with move-by-move threats and defenses. Some authors distinguish static strategic imbalances (e.g. having more valuable pieces or better pawn structure), which tend to persist for many moves, from dynamic imbalances (such as one player having an advantage in piece development), which are temporary. This distinction affects the immediacy with which a sought-after plan should take effect. Until players reach Master-level chess skill, chess tactics tend to ultimately decide the outcomes of games more often than strategy. Many chess coaches thus emphasize the study of tactics as the most efficient way to improve one's results in serious chess play.

The most basic way to evaluate one's position is to count the total value of pieces on both sides. The point values used for this purpose are based on experience. Usually pawns are considered to be worth one point, knights and bishops three points each, rooks five points, and queens nine points. The fighting value of the king in the endgame is approximately four points. These basic values are modified by other factors such as the position of the pieces (e.g. advanced pawns are usually more valuable than those on their starting squares), coordination between pieces (e.g. a bishop pair usually coordinates better than a bishop plus a knight), and the type of position (knights are generally better in closed positions with many pawns, while bishops are more powerful in open positions).

Another important factor in the evaluation of chess positions is the pawn structure or pawn skeleton. Since pawns are the most immobile and least valuable of the pieces, the pawn structure is relatively static and largely determines the strategic nature of the position. Weaknesses in the pawn structure, such as isolated, doubled, or backward pawns and holes, once created, are usually permanent. Care must therefore be taken to avoid them unless they are compensated by another valuable asset, such as the possibility to develop an attack.

A material advantage applies both strategically and tactically. Generally more pieces or an aggregate of more powerful pieces means greater chances of winning. A fundamental strategic and tactical rule is to capture opponent pieces while preserving one's own.

Bishops and knights are called minor pieces. A knight is about as valuable as a bishop, but less valuable than a rook. Rooks and the queen are called major pieces. Bishops are usually considered slightly better than knights in open positions, such as toward the end of the game when many of the pieces have been captured, whereas knights have an advantage in closed positions. Having two bishops (the bishop pair) is a particularly powerful weapon, especially if the opposing player lacks one or both of their bishops.

Three pawns are likely to be more useful than a knight in the endgame, but in the middlegame, a knight is often more powerful. Two minor pieces are stronger than a single rook, and two rooks are slightly stronger than a queen. The bishop on squares of the same color as the opponent's king is slightly more valuable in the opening as it can attack the vulnerable square f7 (for White) or f2 (for Black). A rook is more valuable when doubled with another rook or queen; consequently, doubled rooks are worth more than two unconnected rooks.

One commonly used simple scoring system is:

Under a system like this, giving up a knight or bishop to win a rook ("winning the exchange") is advantageous and is worth about two pawns. This ignores complications such as the current position and freedom of the pieces involved, but it is a good starting point. In an open position, bishops are more valuable than knights (a bishop pair can easily be worth seven points or more in some situations); conversely, in a closed position, bishops are less valuable than knights. A knight in the center of the board that cannot be taken, however, is known as a knight outpost and threatens several fork instances. In such a case, a knight is worth far more than a bishop. Also, many pieces have a partner. By doubling up two knights, two rooks, rook and queen, or bishop and queen, the pieces can get stronger than the sum of the individual pieces alone. When a piece loses its partner, its value slightly decreases. The king is priceless since its capture results in the defeat of that player and ends that game. However, especially in the endgame, the king can also be a fighting piece, and is sometimes given a fighting value of three-and-a-half points.