Backgame Advanced Strategy

This is the second part of our backgame series. If you have not read it yet, start with introduction to the backgame. Here we look more closely at timing, the doubling cube and the choice of anchors.

Timing

Timing measures how long a player can keep the structure he wants, such as a prime or his anchors, before he is forced to give something up. For the backgame player timing is critical. His goal is to hit a checker late in the game and contain it, so by the time the first shot comes he should already have a strong home board, or be close to one.

If your timing is running out and you still have not hit a shot, you are in trouble. You will soon have to break your board or your anchors, and when the shot finally comes you will have nothing left to contain the checker with. At that stage the danger of losing a gammon is very real, and if your opponent doubles, passing is often right.

Counting backgame timing

In most positions timing is counted all the way down to the ace point. In a backgame it is counted differently: you count how many pips your free checkers can travel before they reach the best home board you can still build.

With two anchors in the opponent's board, four of your fifteen checkers are tied up there, which leaves eleven. Eleven checkers are enough for five home points plus one spare. So picture that best final board, then for each free checker count the pips to its place in it, and add them up. The total is your timing: the number of pips you can play while you wait for a shot without breaking anything that matters.

A few details:

• Checkers on your midpoint usually supply most of your timing, because they are farthest from home.
• Moving a checker that already sits where it belongs breaks your board, so it does not add timing.
• Compare your timing with the number of pips your opponent needs to bring his checkers home. If he will be bearing off long before you would have to break, your timing is good.

Cube decisions

Many backgames end with a double that one side passes, so timing is important precisely because it decides takes and passes. But there are other signals as well.

For the race leader, a good time to double is when his structure in front of the anchors is solid, his checkers are close to home and the bear-off is near. With two anchors still in his board there is usually no need to double early. A full prime combined with poor timing for the backgame player is another strong reason to double.

The backgame player must weigh his timing before taking. If he is thinking about doubling himself, he should ask:

• If I hit a checker, can I contain it?
• What are my chances of hitting a second checker?
• How many checkers has my opponent already borne off?
• Are there gaps in my opponent's block?
• Which anchors do I hold?

The clearest double for the backgame player comes when he has a strong home board, has escaped one or two back checkers and has a hit checker on the bar. Reaching that stage is hard, which is why a well-played backgame is a sign of an experienced player.

Which anchors work best

Not all anchor pairs are equal. Most authors and modern bot rollouts agree on a few broad points:

• Anchors on adjacent or nearby low points, such as the 2- and 3-points or the 1- and 3-points, are traditionally rated among the strongest backgames. They cover many entry and hitting numbers.
• Backgames that include the ace point tend to be weaker, partly because the ace point is so deep that your opponent can bring his checkers in above it with relatively little risk.
• Pairs of higher anchors, such as the 4- and 5-points, act more like holding games: they produce shots earlier, but a hit checker is harder to contain.

The exact value of each pair depends on the rest of the position, so check concrete cases with GNU Backgammon or eXtreme Gammon rather than relying on fixed numbers.

A warning for beginners

Experienced players sometimes steer a game toward a backgame against newcomers, because a beginner rarely knows how to play against one. The pattern is familiar: the stronger player leaves easy shots early on, the beginner hits checker after checker, and suddenly the stronger player has two good anchors deep in the beginner's board, for example on the 2- and 3-points.

A useful rule: do not hit a blot if doing so makes it easy for your opponent to establish two strong anchors in your board, unless the hit brings you a major gain. Build your own board instead. That leaves your opponent with only three checkers back for some time, often long enough for you to complete your position and avoid the backgame altogether. See saving the gammon for what to do if your own backgame fails.