Backgammon is a race game where each player tries to take their checkers off the board faster than the other player. Each player has fifteen checkers, set up in a mirror position on a board of 24 triangles (points), using dice and a doubling cube.
The Objective
The objective is to move all of your fifteen pieces into your home quadrant of six points and then take them all off the board before your opponent achieves that same goal.
Basic Movement
The movement of pieces is dictated by the number of spots on each of the two dice rolled. To determine who moves first, each player rolls one die. The player with the higher number plays both numbers, moving either one checker or two separate checkers the corresponding number of spaces. In case of a tie, each player rolls again until the numbers differ.
You can only move your pieces forward in a horseshoe fashion. If your home board is on the right side, you move from right to left on the top and left to right on the bottom. Your opponent moves in the opposite direction.
After each move, you can move either one checker the total of both dice or two separate checkers corresponding to each individual die. For example, if you roll a 3-1 you may move a single checker four spaces, or one checker three spaces and another one space.
Doubles
If you roll the same number on both dice (a "double"), you must move that number four times. For example, double threes means you move three spaces four separate times, distributed among your checkers however you choose, as long as the total equals 12 spaces moved.
Landing Rules
You may land on any empty point, any point where you have your own checkers, or any point where your opponent has exactly one checker (a blot). You cannot land on a point where your opponent has two or more checkers - they control that space.
Points and Defensive Control
When you have two or more checkers on a single point, your opponent cannot land there. This gives you defensive control over that point. Building consecutive points creates a blockade or prime.
Your opponent may not add dice numbers together to jump over a prime. They must move each die separately. A six-point prime is impassable since the highest number on a single die is six.
Making a prime is not foolproof - your opponent will likely be trying to build one too. These "prime versus prime" battles are among the most complex and fascinating aspects of the game.
Hitting and the Bar
A single checker (blot) is vulnerable to being displaced when your opponent rolls a number that lands exactly on that space. The displaced checker goes to the bar - the raised dividing line between the two halves of the board.
To re-enter from the bar, you must place checkers on your opponent's home board if the number on the die corresponds to a point not controlled by your opponent. You may land on empty spaces, your own checkers, or your opponent's blots (hitting them back). You cannot land on your opponent's defensive points.
If you cannot enter at all - that's called "dancing," "fanning," or "bouncing" - your turn is over. You must enter all checkers from the bar before making any other moves.
Bearing Off
Once all your checkers are in your home board, you may begin bearing off - removing checkers based on your dice rolls. Roll a 6-4 and you can take a checker off the 6-point and one off the 4-point.
If you have no checkers on the point matching a die, you take from the highest occupied point. You must play both numbers if possible. You may play either die first, even if it means you can't use the full value of the second die.
Bearing off against no interference is straightforward, but when your opponent has checkers in your home board, many of your moves may be uncomfortable, exposing blots or creating awkward positions.
The Doubling Cube
As in poker, backgammon has a way of "raising" - the doubling cube. Before your roll on any turn, you may turn the cube to double the stakes. The advantage is playing for twice as much; the disadvantage is that your opponent then owns the cube and is the only one who can redouble.
The cube begins in the middle and stays there until someone turns it. Your opponent may take (accept the double and continue) or drop (decline and lose the current stake value).
Gammons and Backgammons
The gammon bonus occurs when you bear off all your checkers while your opponent has taken none off - you win double the cube value. The backgammon bonus (triple game) occurs when you bear off all checkers while your opponent has none off and still has a checker in your home board or on the bar.
In tournament play, you don't need to turn the cube to win gammon or backgammon bonuses. In money play, the Jacoby rule (invented by Oswald Jacoby) requires the cube to be turned for these bonuses to apply.
Beavers and Raccoons
In money games, a beaver occurs when your opponent doubles you and you believe they're actually losing - you can immediately redouble while keeping the cube. A raccoon is re-raising after a beaver. These conventions are not used in tournament play.
Tournament vs. Money Play
Tournament backgammon is played to a set number of points. As you approach the target, games take on higher significance, and eventually it could reach a point where both players are effectively "all in" - whoever wins the next game wins the match.
Points won are calculated by multiplying the cube value by the game type: single (1x), gammon (2x), or backgammon (3x). For example, cube on 8 with a gammon win = 16 points.
Improving Your Game
Backgammon by Paul Magriel is considered a classic beginner text and is highly recommended for anyone interested in taking up the game. Books by Bill Robertie, Kit Woolsey, and Walter Trice serve more advanced players.
Neural net programs known as "bots" - including Snowie, Jellyfish, and GNU Backgammon - play at a high level and can analyze single positions or entire matches. GNU is free and quite capable; Snowie and Jellyfish cost more but are well worth the investment if you plan to study seriously.
Play well and have fun!
By Steve Sax