Backgammon is a simple game with deep strategic elements.
It does not take long to learn to play, although obscure situations do
arise which require
careful interpretation of the 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 she won three in a row and I
lost the match,
three points to two."
In short,
players are trying to get all of their pieces past
their opponent's pieces.
This is difficult because the pieces are scattered at first, and may be
blocked or captured
by the opponent's pieces.
Each side of
the board has a track of twelve adjacent spaces,
called points and 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 checkers always moving from
higher-numbered
points to lower-numbered points. The two players move their checkers 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 perspective of one
player.
Each player
begins with two checkers on his 24-point, three
checkers on his 8-point,
and five checkers each on his 13-point and his 6-point.
Note that the
board as shown can 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 both ways.
Points one to
six, where the player wants to get his pieces to,
are called the home board.
A player may not bear off any checkers unless all of his checkers 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.
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 checkers
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 checkers, he forfeits his turn.
However,
a player must play both dice if it is possible. 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.)
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 checkers 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 checkers or by
friendly checkers.
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
occupied by two or more
enemy checkers. Thus no point is ever occupied by checkers from both
players
at the same time.
Checkers on the
bar 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
checkers on the bar may not move any other checkers until all of the
checkers on the bar
have re-entered the opponent's home field.
When all of a
player's checkers are in his home board, he may
remove them from the board,
or bear 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 checkers from a lower
point unless there
are no checkers 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 checkers 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
checkers
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 checkers by the time his
opponent has borne off all fifteen,
he has lost a gammon, which counts for twice a normal loss. If a
player has not borne off any
checkers, and still has checkers on the bar and/or in his opponent's home
board by the time
his opponent has borne off all fifteen, he has lost 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 usually 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 exclusively
to the player who last
accepted 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.
Beavers
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 usually not allowed in matches.
Jacoby Rule
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 not used in match
play
Crawford Rule
The Crawford
Rule makes match play 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 towards 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 use 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.
Automatic Doubles
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 (upon agreement).
They are never used in match play.
