Backgammon is a board game for two players.
Each player has fifteen pieces or men which move between twenty-four triangles (points) according to the roll of the two dice. The objective of the game is to be first to bear off, that is, to move all fifteen men off the board.
Though the gameplay is quite basic—each player is trying to move his men to his home board and then bear them off before his opponent is able to do so,.backgammon incorporates strategy as with each dice roll, the player must choose between multiple options for movement of the men. Furthermore, the doubling cube, which raises the stakes of the present game when a match consists of multiple games, and rules like the Crawford Rule and the Jacoby Rule, introduce more strategy into the game. Experts have also come up with a standard set of names to define commonly used general strategies for backgammon play such as the running game and the backgame.
As with chess, backgammon has been significantly interfaced with computer technology. By 1979, Hans Berliner's BKG 9.8 program had defeated a world champion backgammon player, and since then neural network and other approaches have improved the playing ability of the virtual backgammon opponent. In addition, a number of other computer programs, most notably of which is called Snowie, have combined the capabilities of an intelligent opponent with extensive statistical analyses of individual moves and the resulting possible outcomes.
Tabula players, from the 13th century.
The ancient Egyptians played a game called senet, which resembled backgammon,with moves controlled by the roll of dice. The Royal Game of Ur, played in ancient Mesopotamia, is a more likely ancestor of modern tables games. Recent excavations at the "Burnt City" in Iran showed that a similar game existed there around 3000 BC. The artifacts include two dice and 60 pieces, and the set is believed to be 100 to 200 years older than the sets found in Ur.
The ancient Romans played a number of games with remarkable similarities to backgammon. Ludus duodecim scriptorum ("game of twelve lines") used a board with three rows of 12 points each, and the pieces were moved across all three rows according to the roll of dice. Not much specific text about the gameplay has survived.Tabula, meaning "table" or "board", was a game mentioned in an epigram of Byzantine Emperor Zeno (AD 476–481). It was similar to modern backgammon in that a board with 24 points was used, and the object of the game was to be the first to bear off all of one's checkers. Three dice were used instead of two, and opposing checkers moved in opposite directions.
In the 11th century Shahnameh, the Persian poet Ferdowsi credits Burzoe with the invention of the tables game nard in the 6th century. He describes an encounter between Burzoe and a Raja visiting from India. The Raja introduces the game of chess, and Burzoe demonstrates nard, played with dice made from ivory and teak.
The jeux de tables, predecessors of modern backgammon, first appeared in France during the 11th century and became a frequent pastime for gamblers. In 1254, Louis IX issued a decree prohibiting his court officials and subjects from playing the games. Tables games were played in Germany in the 12th century, and had reached Iceland by the 13th century. While it is mostly known for its extensive discussion of chess, the Alfonso X manuscript Libro de los juegos, completed in 1283, describes rules for a number of dice and tables games. By the 17th century, tables games had spread to Sweden. A wooden board and checkers were recovered from the wreck of the Vasa among the belongings of the ship's officers.
In the 16th century, Elizabethan laws and church regulations had prohibited playing tables, but by the 18th century backgammon was popular among the English clergy. Edmund Hoyle published A Short Treatise on the Game of Backgammon in 1743; this book described the rules of the game and was bound together with a similar text on whist.
The most recent major development in backgammon was the addition of the doubling cube. It was first introduced in 1926 or 1927 in New York City among members of gaming clubs in the Lower East Side. The cube required players not only to select the best move in a given position, but also to be able to estimate their probability of winning from that position, transforming backgammon into the game it is today.
Backgammon set from the 19th century
Backgammon is a simple game with complicated strategic elements. It does not take long to learn to play, although obscure situations do arise which require careful interpretation of the governing rules. The playing time for each individual game is short, so it is often played in matches, for example the first to five points. Game and match are used in Backgammon to refer to these distinct elements, as in, "I won two games in a row, but then he won three in a row and I lost the match, 3 points to 2."
In short, players are trying to get all of their men past their opponent's pieces. This is difficult because the pieces are scattered at first, and can be blocked or captured by the opponent's men.
Each side of the board has a track of twelve adjacent spaces, called points and these are usually represented by long triangles of alternating (but meaningless) color. The tracks are imagined to be connected across the break in the middle and on just one edge of the board, making a continuous line (but not a circle) of twenty-four points. The points are numbered from 1 to 24, with men always moving from higher-numbered points to lower-numbered points. The two players move their men in opposite directions, so the 1-point for one player is the 24-point for the other. Some recorded games, however, keep the numbering of the points constant from the point of view of one player.
Each player begins with two men on his 24-point, three men on his 8-point, and five men each on his 13-point and his 6-point.
Note that the board as shown may be flipped horizontally, with starting positions and direction of play likewise flipped but with no changes to the mechanics of gameplay. The two orientations are equally common and game boards are all designed to be played in both ways.
Points one to six, where the player wants to get his pieces to, are called the home board or inner board. A player may not bear off any men unless all of his men are in his home board. Points seven to twelve are called the outer board, points thirteen to eighteen are the opponent's outer board, and points nineteen to twenty-four are the opponent's home board. The 7-point is often referred to as the bar point and the 13-point as the mid point.
At the start of the game, each player rolls one die. Whoever rolls higher starts his first turn using the numbers on the already-rolled dice. In case of a tie, the players roll again. The players alternate turns and roll two dice at the beginning of each turn after the first.
After rolling the dice a player must, if possible, move men the number of points showing on each die. For example, if he rolls a 6 and a 3, he must move one checker six points forward and another one three points forward. The dice may be played in either order. The same checker may be moved twice as long as the two moves are distinct: six and then three, or three and then six, but not nine all at once.
If a player has no legal moves after rolling the dice, because all of the points to which he might move are occupied by two or more enemy men, he skips his turn. However, a player must play both dice if it is possible to do so. If he has a legal move for one die only, he must make that move and then forfeit the use of the other die. (If he has a legal move for either die, but not both, he must play the higher number shown.)
If a player rolls two of the same number (doubles) he must play each die twice. For example, upon rolling a 5 and a 5, he must play four men forward five spaces each. As before, a checker may be moved multiple times as long as the moves are distinct.
A checker may land on any point occupied by no men or by friendly men. Also it may land on a point occupied by exactly one enemy checker (a lone piece is called a blot). In the latter case the blot has been hit, and is temporarily placed in the middle of the board on the bar, i.e., the divider between the home boards and the outfields. A checker may never land on a point held by two or more enemy men. Thus no point is ever occupied by men from both players at the same time.
Men on the bar can re-enter the game through the opponent's home field. A roll of 1 allows the checker to enter on the 24-point, a roll of 2 on the 23-point, etc. A player with one or more men on the bar may not move any other men until all of the men on the bar have re-entered into the opponent's home field.
When all of a player's men are in his home board, he may remove them from the board, this is referred to as bearing them off. A roll of 1 may be used to bear off a checker from the 1-point, a 2 from the 2-point, etc. A number may not be used to bear off men from a lower point unless there are no men on any higher points. For example, a 4 may be used to bear off a checker from the 3-point only if there are no men on the 4-, 5-, and 6-points.
A checker borne off from a lower point than indicated on the die still counts as the full die. For instance, suppose a player has only one checker on his 2-point and two men on his 1-point. Then on rolling 1-2, he may move the checker from the 2-point to the 1-point (using the 1 rolled), and then bear off from the 1-point (using the 2 rolled). He is not required to maximize the use of his rolled 2 by bearing off from the 2-point.
If one player has not borne off any men by the time his opponent has borne off all fifteen, he concedes a gammon, which counts for twice a normal loss. If a player has not borne off any men, and still has men on the bar, or in his opponent's home board by the time his opponent has borne off all fifteen, or both, he has concedes a backgammon, which counts for triple a normal loss. Sometimes a distinction is made between pieces in the opponent's home board (triple loss) and pieces on the bar (quadruple loss).
The doubling cube
To speed up match play and to increase the intensity of play and the need for strategy, a doubling cube is used. A doubling cube is a 6 sided die that instead of the numbers 1, 2, 3, 4, 5, 6 on it, has the numbers 2, 4, 8, 16, 32, 64 on it. If a player believes his position to be superior he may, before rolling the dice on his turn, double, i.e., demand that the game be played for twice the current stakes. The doubling cube is placed with the 2 side face up to show that the game's value has been doubled. His opponent must either accept the challenge or resign the game on the spot. Thereafter the right to redouble (double again) belongs solely to the player who was the last to accept a double. If this occurs, the cube is placed with the face of the next power of 2 showing.
The game rarely is redoubled beyond 4 times the original stake, but there is no theoretical limit on the number of doubles. Even though 64 is the highest number on the doubling cube, the stakes may rise to 128, 256, 512 and so on.
A common rule allows beavers - the right for a player to immediately redouble when offered the doubling cube, while retaining the cube instead of giving it back up. (The redouble must be called before the originally doubling player rolls the dice.) In this way, the stakes of the game can rise dramatically.
Beavers are commonly allowed when backgammon is played for money game by game, and is usually not allowed in matches.
The Jacoby Rule makes gammons and backgammons count for their respective double and triple points only if there has been at least one use of the doubling cube in the game. This encourages a player with a large lead in a game to double, and thus likely end the game, rather than see the game out to its conclusion in hopes of a gammon or backgammon. The Jacoby Rule is widely used in money play, but is never used in match play.
The Crawford Rule makes match play much more fair for the player in the lead. If a player is one point away from winning a match, his opponent has no reason not to double; after all, a win in the game by the player in the lead would cause him to win the match regardless of the doubled stakes, while a win by the opponent would benefit twice as much if the stakes are double. Thus there is no advantage in winning the match to being one point shy of winning, if one's opponent is two points shy!
To remedy this situation, the Crawford Rule requires that when a player becomes one single point short of winning the match, neither player may use the doubling cube for a single game, called the Crawford Game. As soon as the Crawford Game is over, any further games can utilise the doubling cube normally.
Not quite as universal as the Jacoby Rule, the Crawford Rule is widely used and generally assumed to be in effect for match play.
When automatic doubles are used, any re-rolls that players must make at the very start of a game (when each player rolls one die) have the side-effect of causing a double. Thus, a 3-3 roll, followed by a re-roll of 5-5, followed by a re-roll of 1-4 that begins the game in earnest, will cause the game to be played from the start with 4-times normal stakes. The doubling cube stays in the middle, with both players having access to it. The Jacoby Rule is still in effect.
Automatic doubles are common in money games and solely upon agreement. They are never used in match play.
A known variant - all same but 6-6 triples rather than doubles stakes.
Five Basic Strategies
Here are the five strategies that are frequently used. You need to be able to switch strategies instantly as the course of the game unfolds.
The Running Game
The most direct, and frequently the best strategy is simply to avoid being hit, trapped, or getting into mutually blocked stand-offs. Obviously, the running game is most desirable when the player is ahead in the race.
The Holding Game
The player keeps a point, high in his opponent's board or on his opponent's bar point, while he builds his board. The player may win by hitting an opponent's blot from the held point, or by rolling large doubles that allow the player to break the point and take the racing lead.
The Priming Game
This involves creating a 6-long wall of men, or at least as long as you are able to make, to block in the opponent's men that are behind the blockade. You can build the wall anywhere between your 11-point and your 2-point and then move it into your home board as the game proceeds.
This involves closing your home board as quick as possible while keeping your opponent trapped on the bar. For example, if your opponent rolls an early 2 and moves one checker from your 1-point to your 3-point and you then roll a 5-5, you can play 6/1 6/1 8/3 8/3. Your opponent is now in serious trouble because they have 2 men on the bar and you have already closed half your inner board.
This is where you have 2 or more anchors in your opponent's home board. (An anchor is a point occupied by at least 2 of your men.) It should be used when you are significantly behind as it much improves your chances. The best places for anchors are towards your opponent's lower point and either on adjacent points or with a single point in between. Timing is crucial for an effective backgame: after all, there's no point having 2 nice anchors and a solid wall in your own home board if you are then forced to dismantle this straight away, while your opponent is getting their men home, because you don't have other spare men to move! In this case, it's better to have men on the bar so that you can preserve your position until your opponent gives you a chance to hit, so it can be a good idea to try and get your opponent to hit them in this case!
Some people go for a backgame from the outset, but this is a mistake. The backgame is a losing strategy: it's just that this strategy makes you less likely to lose if you are already losing!
A few turns from the beginning of a sample game will illustrate the rules of movement. To start the game blue rolls a 4 and green rolls a 1, so blue takes the first turn playing a 4,1. This is an unfavorable opening roll, arguably the worst possible, but blue uses it the best he can. He takes a checker from each of his heavy points by playing 13-9, 6-5.
It is seldom useful to have five men on the same point, so blue starts to spread his men around. He is threatening to build a prime, i.e., a blockade to prevent green's two trailing men from getting home. The disadvantage of blue's choice is that it isn't very safe. It leaves two blots which green might hit. Some experts prefer the less aggressive but safer move of 24-23, 13-9.
Green rolls a 4, 4. This is an very lucky roll. Not only can he hit both of blue's blots with 1-5*-9*, he also has two more fours to play. He may, for example play 19-23(2), moving two men from his 6-point to the 2-point. This leaves blue with two men on the bar, trying to re-enter against green's home board, which has two points blocked by the green player.
Green was smart to hit twice, because it disrupts blue's efforts to build a prime, and it puts blue considerably behind in the game. Those two men must come all the way around the board before blue can begin to bear his men off.
In contrast, green's decision to make the 2-point was strategically unsound. Though it may prevent blue from entering with both men, and there is some chance green will be able to build a strong home board before blue gets organized, increasing the chances of winning a gammon, the disadvantage is that green will now find it difficult to build a prime. If blue manages to make an advanced anchor, i.e., get two of his back men on green's 3-, 4-, or especially the 5- point, then green's blocking game is busted.
Green would be in better shape had he played 12-16(2), keeping open the option to block or attack depending on blue's next roll.
Blue rolls 5, 2. The only legal move is Bar-20. The two can't be played from the bar because green owns his 2-point, and until blue has played all his men off the bar, he can't play anywhere else. Therefore the 2 is forfeited and blue's turn is over.
Green got what he wanted, in that blue was not able to enter both men, but the fight is far from over. Green must hit the blot on his next roll, or else blue has a fifty-fifty chance to cover his blot and take a fairly strong position. Even if green does hit, blue has many rolls to hit back. A war for green's 5-point will shape the character of the game in the near future.
Backgammon is often played for money stakes. The most common ways that gamblers play is to set a wager on which player can be first to reach a certain number of points, achieved over however many games necessary; to assign a dollar value to each point, and to play until a certain number of points is reached or passed; or to assign a dollar value to each point and play games until either player chooses to stop.
A chouette is an adapted form of backgammon for three or more players, generally played for money.
Before beginning the game , a monetary value is agreed upon for the value of each point. Dice throws determine an initial ranking. One player is in the box, the next is the captain, and the others take their places as members of the captain's team. The captain, who may take advice from the team, plays against the player in the box. Traditionally, there is one doubling cube. This is controlled by the player in the box and the captain (in the usual way), except that, when the player in the box offers a double, each member of the team may accept or decline independently. Nowadays, however, the team members often use separate doubling cubes, in which case they may either accept, decline and offer doubles independently. Whichever system is used , a team member who has refused a double drops out of the game and may no longer give any advice to the captain. If the captain drops out of the game, the highest ranking team member takes over as captain.
At the end of each game, the box settles up with the other players as individuals . If the player in the box has won, he retains the box and the (original) captain becomes the lowest ranking team member. If the (final) captain has won, he takes over from the player in the box, who joins the team as its lowest ranking member. The highest ranking member of the team becomes its captain for the next game.
[The word 'chouette' is French for any of a seemingly arbitrary collection of species of typical (i.e. non-barn) owls.]
Backgammon throughout the Middle East and Central Asia
Backgammon is played a lot in the Middle East and Central Asia, particularly in cafes. There are four main variants played in the Middle East:
1) the European game as described above and known as ifranjiah (meaning Frankish in Arabic); "Takhte Nard" is the Iranian version.
2) shesh besh (Shesh means six in Persian & Hebrew and Besh means five in Turkish) in Azerbaijan, Israel, and Uzbekistan and tavla in Turkey;
3) mahbusa (meaning 'imprisoned')
The most popular of those is probably mahbusa. In this game each player's 15 men are all initially positioned on his 24-point. When hit, an isolated checker is not placed on the bar. Rather the hitting piece sits on top of the hit piece forming a block, i.e. the same rules apply as if the point was occupied by two or more pieces of the same colour. The checker which has been hit is 'imprisoned' and cannot be moved until the opponent removes his piece: hence the name of the game. Sometimes a further rule requires that a player must bring his first checker to the opponent's home board before moving any other men. Whether or not this rule is applied, a rapid advance to the opponent's side of the board is desirable as imprisoning the opponent's men on his home table is highly advantageous.
An interesting feature of backgammon as played in some Arab countries is that Persian or Kurdish numbers, rather than Arabic ones, are called out by a player announcing his dice rolls.
People in Iranian plateau and Caucasus region, especially in Iran, Armenia, Azerbaijan, and Georgia, are very fond of playing Narde. In Georgia they play mainly the "short Narde", a slightly simplified version of ifranjiah. In Iran it is called "Takhte Nard". In Armenia and Azerbaidjan experienced players prefer to play "long Narde", which requires more skill and even "knowledge" of some non-written strategic methods. As in 'mahbusa' all 15 men of a player are initially positioned on his 24-point, but there is a principal difference. One is forbidden to put his checker at a point occupied by opponent's checker. So there is no "hitting" and no "imprisonment" in the long Narde game. The main strategy is to secure playing "big pairs" by one's own men and prevent as much as possible doing the same by the opponent.
A Swedish variant of backgammon, also called Swedish Tables in English.
The main difference compared to other backgammon variants is the method of winning. You can win by bearing off, but there are also several other ways to win, such as to arrange all your men in certain pre-determined patterns or by hitting so many men that your opponent can not bring them in again.
Brädspel is played without the doubling cube.
Gul bara is also called ‘Rosespring Backgammon’ or ‘Crazy Narde’ and mistakingly called ‘Gul Bahar’ in some Arab countries.
Old English Rule
This rule limits the number of men to a maximum of five on each point, thus restricting some moves that might otherwise be made. This variation of backgammon is popular in England (as well as other regions), and is viewed as making the gameplay more interesting.
The Runte Rule allows the player to move his men both backwards and forwards within his own home board. The player cannot move the checker in such a way that it lands outside of his home board. The rule was created to increase the possibility of scoring backgammons and gammons, because it allows one to trap the opponent for longer.
In Greece, backgammon is called tavli (related to the word tavla 'board, table', and cognate to the Latin Tabula). It consists of three main styles, Portes, Plakoto and Fevga. Portes resembles the standard game, with minor variations. Plakoto is very similar to mahbusa or Tapa, while Fevga is similar to Narde or the Turkish variant Moultezim. The three are normally played consecutively, one after another, in matches of three, five or seven points.
In Republic of Macedonia the game is called tabla (табла, meaning 'board, table'). It also consists of three main styles, very similar to the Greek tavli: Tabla, Gjul Bara and Tapa. They are played consecutively (in that order) in a match of five. The first game Tabla (Табла) is the standard backgammon, with few differences: there are no doubling cubes and there is no backgammon (it's the same as gammon). Gjul Bara (Ѓул Бара) and Tapa (Тапа) are played the same way as described before. Gammon is called mars (марс) and it's the only situation when a player can win 2 points with a single game. Mars is present in all three styles. When starting the match, each player rolls one die, to determine who will start. If it's a tie, the players roll again. But, unlike the regular backgammon, the already-rolled dice are disregarded and the player that won the first turn, rolls both dice to begin. In the next game in the match, the player that won the previous has the first turn.
Long Gammon is a variant of backgammon, the only difference being that all fifteen of the players' men start on their opponent's one-point. All other rules of the game are the same as in regular backgammon.
The first strong computer opponent was BKG 9.8. It was programmed by Hans Berliner in the late 1970s on a PDP-10 as an experiment in evaluating backgammon positions. Early versions of BKG played very badly even against poor players, but Berliner noticed that the critical mistakes the program made were always at phase changes. He applied basic principles of fuzzy logic in order to smooth out the transition between phase changes, and by July 1979, BKG 9.8 was ready to play against then current world champion Luigi Villa. It won the match, 7-1, becoming the first computer program to defeat a world champion in any game, although this was mostly a matter of luck, as the computer happened to get better dice rolls than its opponent did in that match.
Beginning in the late 1980s, creators of backgammon-playing software began to have even more success with a neural network approach. TD-Gammon, developed by Gerald Tesauro of IBM, was the first of these computer programs to play at or close to the expert level. This program's neural network was trained using Temporal Difference learning applied to data generated from self-play.
This line of research has resulted in two modern commercial programs, Jellyfish and Snowie, the shareware BGBlitz , and the free software GNU Backgammon, that play on a par with the best human backgammon players in the world. It is worth noting that without their associated "weights" tables which represent hours or even months of tedious neural net training, these programs play no better than a human child would.
It is interesting to compare the development of backgammon software with that of modern chess software:
- For backgammon, neural networks work better than any other methods so far tried. For chess, brute force searching, with sophisticated pruning and other refinements, works better than than using neural networks.
- Every advance in the power of computer hardware has significantly improved the strength of chess programs. In contrast to this , additional computing power appears to improve the strength of backgammon software only slightly.
- For both backgammon and chess, it is at present unclear whether the best computer or the best human is the best player overall.
Backgammon software has been developed not only to play and analyze games, but also to facilitate play between humans from different parts of the world over the internet. Dice rolls are provided by random or pseudorandom number generators. Real-time on-line play began with the First Internet Backgammon Server on July 19, 1992. The server is the longest running non-commercial backgammon server and enjoys a strong international community of backgammon players. Several commercial websites also offer online real-time backgammon play, the leading three being Gammon Empire and Play65 who began operations in January 2005 followed by Partygammon who launched their online backgammon product in June 2006.
See our Backgammon Glossary for an explanation of the common terms and expressions used in backgammon.