Cash game. Center cube. White on move.

(A) White to play 6-1.

(B) White to play 6-1.

One of the most difficult choices in the early and middle stages of a backgammon game is the choice between creating structure (a blocking prime) and attending to issues on the other side of the board. Those issues vary: you might be able to hit a checker, or make a defensive anchor, or escape one of your back men. In some cases, making structure is correct. In other cases, playing on the other side of the board is correct. Let’s take a look at a couple of examples, to see the ideas that have to guide us in these decisions.

Let’s start with Position (A). It’s not a tough problem. White can hit a blot with 24/17* or build some structure with 13/7 8/7. The structural play has two problems: the structure isn’t that impressive, and it gives Black a direct shot at White’s blot on the 14-point. For structure to trump hitting, you want structure which is solid and imposing.

24/17* might look loose, but it accomplishes two great things: hitting an important blot, and escaping a rear checker. True, Black may hit back. He has a total of 16 return hits (all twos except 2-6, and all fives except 5-6). But that leaves 20 rolls that don’t hit, and those are great rolls for White – he’s ahead in the race and his rear checkers are out. Potentially getting all your back checkers out is a great result, and 24/17* puts White within striking distance of that goal.

Problem (B) occurs much later in the game. White has two choices: he can block in Black’s two rear checkers with 13/7 8/7, or he can escape his own last checker with 24/17. Running out is more volatile – if White gets away with it, he’s close to a double, but if Black hits, White is an immediate underdog. Making the 7-point, on the other hand, leaves White a solid but unspectacular favorite in most variations.

What’s right? White should go ahead and make his 7-point. There are two reasons:

(1) With an advantage and a centered cube, you’re not looking to make big swing plays. You’re more interested in plays that preserve your advantage and creep closer to an eventual good double. When in doubt between the merits of two plays, lean to the more conservative choice.

(2) Trapping two men will increase your gammon chances dramatically. There’s actually not much difference in raw winning chances between the two plays, but locking in Black’s two back checkers will win many more gammons.

The basic idea in these positions is a simple one: the quality of the structure you build is crucial. Turning a very weak structure into a slightly better structure, as in Position (A), isn’t worth that much. Turning a broken structure into a 5-point prime, as in Position (B), is huge, even when the alternative is escaping the last checker from behind a 5-prime! The lesson to be learned is that creating a 5-prime or even a 4-prime may outweigh making progress on the other side of the board, but just building a blocking point or a 3-prime is probably not enough.

Cash game. White owns the cube. White on roll.

Should White double? If White doubles, should Black take or drop?

In this position, White took an early cube based on his ownership of Black’s 2-point and the fact that Black still had a checker left to escape. After that, the game developed almost perfectly for him. His deuce-point game caused Black to bear in awkwardly, while White’s front position came together and prevented Black’s back checker from escaping. After Black’s last roll (an awkward 4-4), White finally has a clear advantage, although he still trails by 47 pips in the race. Is this the right time to double?

read more…

Cash game, White owns the cube.

White to play 6-1.

In this position, Black has managed to build a full 6-prime, and White has one checker trapped behind it. A single checker behind a full prime is normally a pretty bad position. If Black could escape all his back checkers and arrange them on top of his prime, while White just filled in his board, Black would be about a 90-10 favorite, with gammon chances in the 5% to 6% range.

Fortunately, Black hasn’t yet escaped all his checkers, which gives White some extra resources. In fact, if he makes the right play here, his winning chances bounce up into the 25% range! That’s a hefty increase, so let’s see if we can figure out the best way to proceed.

read more…

Cash game, White owns the cube.

White to play 5-1.

Root Numbers

In backgammon, a root number is just a dice throw that damages or destroys your position. We mostly encounter these by accident, when we throw an awkward shot that can’t be played except by wrecking our inner board or leaving a bunch of blots somewhere.

Root numbers don’t always happen by accident, however. Sometimes the only way of saving a hopeless position is to notice that by making a certain play, you can create a few root numbers for your opponent which wouldn’t exist otherwise.

read more…

Money game, White owns the cube.

White to play 4-1.

This position is not difficult but it illustrates a key idea in priming games, whether prime against prime or prime against blitz: Do the hardest thing first, and force your opponent to do a hard thing in reply.

By “hard thing” I mean anything that you are a 70-30 underdog (or worse) to do. Usually this implies anything that must be done and which requires a single number on the dice. When we begin thinking in terms of “doing hard things” and “making our opponent do hard things”, complicated positions can start to look pretty simple.

Here, for instance, it’s clear that Black’s prime will not break. Black has to come in from the bar, which might take a while, after which he has the checkers on the 18-point to move, as well as the checker which just entered and the checker on the midpoint. So to win, White will have to escape his rear checker, and that will require an ace (a “hard thing”) plus a six (another “hard thing”). Since he just threw an ace, he wants to play 24/23 if at all possible. Since he can use the four to make both a 5-point board and a 5-prime, that’s his play. He should move 24/23 and 6/2.

What would it take for White to pass up 24/23 with the ace? In most variations of this position, 24/23 will remain correct, but here’s an example where it’s a mistake:

Position A: White to play 4-1.

Without a 5-point board to give Black something “hard” to do, White doesn’t have the security of moving to the 23-point. Here he has to play 2/1, to keep Black on the bar for some time. After that, either 8/4 or 13/9 are about equal.