Draughts or checkers is a group of strategy board games for two players which involve diagonal moves of uniform game pieces and mandatory captures by jumping over opponent pieces. Draughts developed from alquerque. The name derives from the verb to draw or to move.
The most popular forms are English draughts, also called American checkers, played on an 8×8 checkerboard; Russian draughts, also played on an 8×8, and international draughts, played on a 10×10 board. There are many other variants played on 8×8 boards. Canadian checkers and Singaporean/Malaysian checkers are played on a 12×12 board.
English draughts was weakly solved in 2007 by the team of Canadian computer scientist Jonathan Schaeffer. From the standard starting position, both players can guarantee a draw with perfect play.
General rulesDraughts is played by two opponents, on opposite sides of the gameboard. One player has the dark pieces; the other has the light pieces. Players alternate turns. A player may not move an opponent's piece. A move consists of moving a piece diagonally to an adjacent unoccupied square. If the adjacent square contains an opponent's piece, and the square immediately beyond it is vacant, the piece may be captured by jumping over it.
Only the dark squares of the checkered board are used. A piece may move only diagonally into an unoccupied square. When presented, capturing is mandatory in most official rules, although some rule variations make capturing optional. In almost all variants, the player without pieces remaining, or who cannot move due to being blocked, loses the game.
MenUncrowned pieces move one step diagonally forwards, and capture an opponent's piece by moving two consecutive steps in the same line, jumping over the piece on the first step. Multiple enemy pieces can be captured in a single turn provided this is done by successive jumps made by a single piece; the jumps do not need to be in the same line and may "zigzag". In English draughts men can jump only forwards; in international draughts and Russian draughts men can jump both forwards and backwards.
KingsWhen a man reaches the kings row, it becomes a king, and is marked by placing an additional piece on top of the first man, and acquires additional powers including the ability to move backwards and capture backwards. Like men, a king can make successive jumps in a single turn provided that each jump captures an enemy man or king.
In international draughts, kings move any distance along unblocked diagonals, and may capture an opposing man any distance away by jumping to any of the unoccupied squares immediately beyond it. Because jumped pieces remain on the board until the turn is complete, it is possible to reach a position in a multi-jump move where the flying king is blocked from capturing further by a piece already jumped.
Flying kings are not used in English draughts; a king's only advantage over a man is the ability to move and capture backwards as well as forwards.
NamingIn most non-English languages, draughts is called dame, dames, damas, or a similar term that refers to ladies. The pieces are usually called men, stones, "peón" or a similar term; men promoted to kings are called dames or ladies. In these languages, the queen in chess or in card games is usually called by the same term as the kings in draughts. A case in point includes the Greek terminology, in which draughts is called "ντάμα", which is also one term for the queen in chess.
National and regional variants
Russian Column draughtsColumn draughts is a kind of draughts, known in Russia since the beginning of the nineteenth century, in which the game is played according to the usual rules of draughts, but with the difference that the beaten draught is not removed from the playing field, and is captured under the beating figure.
The resulting towers move around the board as a whole, "obeying" the upper draught. When taking the tower, only the upper draught is removed from it. If on the top there is a draught of other colour than removed as a result of fight, the tower becomes a tower of the rival. Rules of moves of draughts and kings correspond to the rules of Russian draughts.
- Russian Wikipedia article on :ru:Столбовые шашки|Russian Column draughts
Flying kings; men can capture backwards
Flying kings; men cannot capture backwards
No flying kings; men cannot capture backwards
SportThe World Championship in English draughts began in 1840. The winners in men's have been from the United Kingdom, United States, Barbados, and most recently Italy. The women's championship in English draughts started in 1993. The women's winners have been from Ireland, Turkmenistan, and Ukraine.
The World Championship in international draughts began in 1885 in France, and since 1948 has been organised by the World Draughts Federation. It occurs every two years. In even years following the tournament, the World Title match takes place. The men's championship has had winners from the Netherlands, Canada, the Soviet Union, Senegal, Latvia, and Russia. The first Women's World Championship was held in 1973. The World Junior Championship has been played since 1971. European Championships have been held since 1965 and 2000.
Other official World Championships began as follows: Brazilian draughts, in 1985; Russian draughts, in 1993; Turkish draughts, in 2014.
- Blue and Gray: On a 9×9 board, each side has 17 guard pieces that move and jump in any direction, to escort a captain piece which races to the centre of the board to win.
- Cheskers: A variant invented by Solomon Golomb. Each player begins with a bishop and a camel rather than, and men reaching the back rank promote to a bishop, camel, or king.
- Damath: A variant utilising math principles and numbered chips popular in the Philippines.
- Dameo: A variant played on an 8×8 board, move and capture rules are similar to those of Armenian draughts. A special "sliding" move is used for moving a line of checkers similar to the movement rule in Epaminondas. By Christian Freeling.
- Hexdame: A literal adaptation of international draughts to a hexagonal gameboard. By Christian Freeling.
- Lasca: A checkers variant on a 7×7 board, with 25 fields used. Jumped pieces are placed under the jumper, so that towers are built. Only the top piece of a jumped tower is captured. This variant was invented by World Chess Champion Emanuel Lasker.
- Philosophy shogi checkers: A variant on a 9×9 board, game ending with capturing opponent's king. Invented by Inoue Enryō and described in Japanese book in 1890.
- Suicide checkers : A variant where the objective of each player is to lose all of their pieces.
- Tiers: A complex variant which allows players to upgrade their pieces beyond kings.
- Vigman's draughts: Each player has 24 pieces – one on the light squares, a second set on dark squares. Each player plays two games simultaneously: one on light squares, the other on dark squares. The total result is the sum of results for both games.
Games sometimes confused with draughts variants
- Halma: A game in which pieces move in any direction and jump over any other piece, friend or enemy, and players try to move them all into an opposite corner.
- Chinese Checkers: Based on Halma, but uses a star-shaped board divided into equilateral triangles.
- Konane: "Hawaiian checkers".
Ancient gamesSimilar games have been played for a millennia.
A board resembling a draughts board was found in Ur dating from 3000 BC. In the British Museum are specimens of ancient Egyptian checkerboards, found with their pieces in burial chambers, and the game was played by Queen Hatasu. Plato mentioned a game, πεττεία or petteia, as being of Egyptian origin, and Homer also mentions it. The method of capture was placing two pieces on either side of the opponent's piece. It was said to have been played during the Trojan War. The Romans played a derivation of petteia called latrunculi, or the game of the Little Soldiers. The pieces, and sporadically the game itself, were called calculi.Kitab al-Aghani. Al qirq was also the name for the game that is now called nine men's morris. Al qirq was brought to Spain by the Moors, where it became known as Alquerque, the Spanish derivation of the Arabic name. The rules are given in the 13th-century book Libro de los juegos. In about 1100, probably in the south of France, the game of Alquerque was adapted using backgammon pieces on a chessboard.
Each piece was called a "fers", the same name as the chess queen, as the move of the two pieces was the same at the time.
CrowningThe rule of crowning was used by the 13th century, as it is mentioned in the Philip Mouskat's Chronique in 1243 when the game was known as Fierges, the name used for the chess queen. The pieces became known as "dames" when that name was also adopted for the chess queen. The rule forcing players to take whenever possible was introduced in France in around 1535, at which point the game became known as Jeu forcé, identical to modern English draughts. The game without forced capture became known as Le jeu plaisant de dames, the precursor of international draughts.
The 18th-century English author Samuel Johnson wrote a foreword to a 1756 book about draughts by William Payne, the earliest book in English about the game.
Computer draughtshas been the arena for several notable advances in game artificial intelligence. In the 1950s, Arthur Samuel created one of the first board game-playing programs of any kind. More recently, in 2007 scientists at the University of Alberta developed their "Chinook" program to the point where it is unbeatable. A brute force approach that took hundreds of computers working nearly two decades was used to solve the game, showing that a game of draughts will always end in a draw if neither player makes a mistake. The solution is for the draughts variation called go-as-you-please checkers and not for the variation called three-move restriction checkers. As of December 2007, this makes English draughts the most complex game ever solved.
Computational complexityCheckers is played on an N × N board.
It is PSPACE-hard to determine whether a specified player has a winning strategy. And if a polynomial bound is placed on the number of moves that are allowed in between jumps, then the problem is in PSPACE, thus it is PSPACE-complete. However, without this bound, Checkers is EXPTIME-complete.
However, other problems have only polynomial complexity:
- Can one player remove all the other player's pieces in one move ?
- Can one player king a piece in one move?