1911 Encyclopædia Britannica/Backgammon

BACKGAMMON, a game played with draughtsmen and a special board, depending on the throw of dice. It is said to have been invented about the 10th century (Strutt). A similar game (Ludus duodecim scriptorum, the “twelve-line game”) was known to the Romans, and Plato (Republic, bk. x.) alludes to a game in which dice were thrown and men were placed after due consideration. The etymology of the word “backgammon” is disputed; it is probably Saxon—baec, back, gamen, game; i.e. a game in which the players are liable to be sent back. Other derivations are, Dan. bakke, tray, gammen, game (Wedgwood); and Welsh bach, little, cammaun, battle (Henry). Chaucer alludes to a game of “tables,” played with three dice, in which “men” were moved from the opponent’s “tables,” the game (ludus Anglicorum) being described in the Harleian MSS. (1527). The French name for backgammon is trictrac, imitative of the rattle of the dice.

Backgammon is played by two persons. The “board” (see diagram) is divided into four “tables,” each table being marked with six “points” coloured differently. The inner and outer tables are separated from each other by a projecting bar. The board (in the ordinary form of the game) is furnished with fifteen white and fifteen black men, “set” or arranged as in the diagram. It is usual to make the inner table the one nearest to the light. Two dice-boxes are required, one for each player, and a pair of dice, which are used by both players. The dice are marked with numbers on their six sides, from one to six, number one being called, “ace”; two, “deuce”: three, “trey.” Formerly the four was called “quatre” (pronounced “cater”); the five, “cinque” (pronounced either “sank” or “sink”); and the six, “six” (size).

For the right to start each player throws one or two dice; the one who throws the higher number has the right of playing first; and he may either adopt the numbers thrown or he may throw again, using both dice.

The men are moved on from point to point, according to the throws of the dice made by the players alternately. White moves from black’s inner table to black’s outer, and from this to white’s outer table, and so on to white’s inner table; and all black’s moves must be in the contrary direction. A player may move any of his men a number of points corresponding to the numbers thrown by him, provided the point to which the move would bring him is not blocked by two or more of his adversary’s men being on it. The whole throw may be taken with one man, or two men maybe moved, one the exact number of points on one die, the other the number on the other die. If doublets are thrown (e.g. two sixes), four moves of that number (e.g. four moves of six points) may be made, either all by one man or separately by more. Thus, suppose white throws five, six, he may move one of his men from the left-hand corner of the black’s inner table to the left-hand corner of black’s outer table for six; he may, again, move the same man five points farther on, when his move is completed; or he may move any other man five points. But white cannot move a man for five from the black’s ace-point, because the six-point in that table is blocked. Any part of the throw which cannot be moved is of no effect, but it is compulsory for a player to move the whole throw unless blocked. Thus if the men were differently placed, and white could move a six, and having done so could not move a five, his move is completed. If, however, by moving the five first, he can afterwards move a six, he must make the move in that manner.

When a player so moves as to place two men on the same point, he is said to “make a point.”

When there is only a single man on a point, it is called a “blot.” When a blot is left, the man there may be taken up (technically the blot may be “hit”) by the adversary if he throws a number which will enable him to place a man on that point. The man hit is placed on the bar, and has to begin again by entering the adversary’s home table again at the next throw should it result in a number that corresponds to an unblocked point. The points in the home tables count for this purpose as 1, 2, 3, 4, 5, 6, beginning from the ace-point. A player is not allowed to move any other man while he has one to enter. It is, therefore, an advantage to have made all the points in your own board, so that your adversary, if you take a man up, cannot enter; and you can then continue throwing until a point is opened.

The game proceeds until one of the players gets all his men into his inner table or home. Then he begins to take his men off the board, or to bear them, i.e. to remove a man from any point that corresponds in number with his throw. If such a point is unoccupied, a move must be made, if there is room for it, and a move may be taken, instead of bearing a man, at any time; but when six is empty, if six is thrown a man may be borne from five and so on. If, after a player has commenced throwing off his men, he should be hit on a blot, he must enter on his adversary’s inner table and must bring the man taken up into his own inner table before he can bear further.

Whoever first takes off all his men wins the game:—a single game (a “hit”) if his adversary has begun bearing; a double game (a “gammon”) if the adversary has not borne a man; and a triple game (a “backgammon”) if, at the time the winner bears his last man, his adversary, not having borne a man, has one in the winner’s inner table, or has a man up. When a series of games is played, the winner of a hit has the first throw in the succeeding game; but if a gammon is won, the players each throw a single die to determine the first move of the next game.

In order to play backgammon well, it is necessary to know all the chances on two dice and to apply them in various ways. The number of different throws that can be made is thirty-six. By taking all the combinations of these throws which include given numbers, it is easily discovered where blots may be left with the least probability of being hit. For example, to find the chance of being hit where a blot can only be taken up by an ace, the adversary may throw two aces, or ace in combination with any other number up to six, and he may throw each of these in two different ways, so that there are in all eleven ways in which an ace may be thrown. This, deducted from thirty-six (the total number of throws), leaves twenty-five; so that it is 25 to 11 against being hit on an ace. It is very important to bear in mind the chance of being hit on any number. The following table gives the odds against being hit on any number within the reach of one or two dice:—

It is	25	to	11,	or about	9	to	4,	against being hit on	1
"	24	"	12,	or	2	"	1,	"	2
"	22	"	14,	or about	3	"	2,	"	3
"	21	"	15,	or	7	"	5,	"	4
"	21	"	15,	"	7	"	5,	"	5
"	19	"	17,	"	91/2	"	81/2,	"	6
"	30	"	6,	"	5	"	1,	"	7
"	30	"	6,	"	5	"	1,	"	8
"	31	"	5,	or about	6	"	1,	"	9
"	33	"	3,	or	11	"	1,	"	10
"	34	"	2,	"	17	"	1,	"	11
"	33	"	3,	"	11	"	1,	"	12

The table shows that if a blot must be left within the reach of one die, the nearer it is left to the adversary’s man the less probability there is of its being hit. Also, that it is long odds against being hit on a blot which is only to be reached with double dice, and that, in that case (on any number from 7 to 11), the farther off the blot is, the less chance there is of its being hit.

The table assumes that the board is open for every possible throw. If part of the throw is blocked by an intervening point being held by adverse men, the chance of being hit is less.

Two principles, then, have to be considered in moving the men:—(1) To make points where there is the best chance of obstructing the opponent. (2) When obliged to leave blots, to choose the position in which they are least likely to be hit.

The best points to secure are the five-point in your own inner table and the five-point in your adversary’s inner table. The next best is your own bar-point; and the next best the four in your own inner table.

The best move for some throws at the commencement of a game is as follows:—Aces (the best of all throws), move two on your bar-point and two on your five-point. This throw is often given to inferior players by way of odds.

Ace, trey: make the five-point in your inner table.

Ace, six: make your bar-point.

Deuces: move two on the four-point in your inner table, and two on the trey-point in your opponent’s inner table.

Deuce, four: make the four-point in your own table.

Threes: play two on the five-point in your inner table, and two on the four-point of your adversary’s inner table, or make your bar-point.

Trey, five: make the trey-point in your own table.

Trey, six: bring a man from your adversary’s ace-point as far as he will go.

Fours: move on two on the five-point in your adversary’s inner table, and two from the five in his outer table.

Four, five and four, six: carry a man from your adversary’s ace-point as far as he will go.

Fives: move two men from the five in your adversary’s outer table to the trey-point in your inner table.

Five, six: move a man from your adversary’s ace-point as far as he will go.

Sixes (the second-best throw): move two on your adversary’s bar-point and two on your own bar-point.

In carrying the men home carry the most distant man to your adversary’s bar-point, to the six-point in your outer table, and then to the six-point in your inner table. By following this rule as nearly

as the throws admit, you will carry the men to your inner table in the fewest number of throws.

Avoid carrying many men upon the trey or deuce-point in your own tables, as these men are out of play.

Whenever you have taken up two of your adversary’s men, and two or more points made in your inner table, spread your other men in the hope of making another point in your tables, and of hitting the man your adversary enters.

Always take up a man if the blot you leave in making the move can only be hit with double dice, but if you already have two of your opponent’s men in your tables it is unwise to take up a third.

In entering a man which it is to your adversary’s advantage to hit, leave the blot upon the lowest point you can, e.g. ace-point in preference to deuce-point.

When your adversary is bearing his men, and you have two men in his table, say, on his ace-point, and several men in the outer table, it is to your advantage to leave one man on the ace-point, because it prevents his bearing his men to the greatest advantage, and gives you the chance of his leaving a blot. But if you find that you can probably save the gammon by bringing both your men out of his table, do not wait for a blot. Eight points is the average throw.

The laws of backgammon (as given by Hoyle) are as follows:—

1. When a man is touched by the caster it must be played if possible; if impossible no penalty. 2. A man is not played till it is placed upon a point and quitted. 3. If a player omits a man from the board there is no penalty. 4. If he bears any number of men before he has entered a man taken up, men so borne must be entered again. 5. If he has mistaken his throw and played it, and his adversary has thrown, it is not in the choice of either of the players to alter it, unless they both agree to do so. 6. If one or both dice are "cocked," i.e. do not lie fairly and squarely on the table, a fresh throw is imperative.

Russian Backgammon varies from the above game in that the men, instead of being set as in the diagram, are entered in the same table by throws of the dice, and both players move in the same direction round to the opposite table. There are various rules for this game. By some a player is not obliged to enter all his men before he moves any; he can take up blots at any time on entering, but while he has a man up, he must enter it before entering any more or moving any of those already entered. If he cannot enter the man that is up, he loses the benefit of the throw.

A player who throws doublets must play or enter not only the number thrown, but also doublets of the number corresponding to the opposite side of the dice; thus, if he throws sixes, he must first enter or move the sixes, as the case may be, and then aces, and he also has another throw. Some rules allow him to play either doublets first, but he must always complete one set before playing the other. If a player cannot play the whole of his throw, his adversary is sometimes allowed to play the unplayed portion, in which cases the caster is sometimes allowed to come in and complete his moves, if he can, and in the event of his having thrown deuce-ace or doublets to throw again. If he throws doublets a second time, he moves and throws again, and so on. The privilege is sometimes restricted by not allowing this advantage to the first doublets thrown by each player. It is sometimes extended by allowing the thrower of the deuce-ace to choose any doublets he likes on the opposite side of the dice, and to throw again. The restriction with regard to the first doublets thrown does not apply to deuce-ace, nor does throwing it remove the restriction with regard to first doublets. A player must first be able to complete the doublets thrown. If the player cannot move the whole throw he cannot take the corresponding doublets, and he is not allowed another throw if he cannot move all the points to which he is entitled.