Do you double?

Backgammon Position:

You are black in the position above. Do you double? If you are white do you take if you are doubled?

Backgammon beginners and many intermediates have a lot of trouble with positions like this. What normally happens is they roll something like 62, played 15/7 and then after white rolls an average number – let’s say 53 played 17/9, black doubles and white passes.

They don’t double before the roll because of thinking that goes something like this: “I’m not favourite to get that checker on my 15-pt to safety and then if it gets hit white has such a strong board that I will have to pass his redouble – I think I’ll wait.”

Now let’s look at how to think about this position correctly. You must check the three key elements of doubling:

The Race – black is ahead 17 pips before the roll so based on the race alone this would be a pass. Advantage to black
Position – black has a 4½ point home board to white’s five point board. Slight edge to white.
Threat – black has significant threats. He could point on white’s blot on his 5-pt. He could hit the white blot on his 8-pt and not be hit back. He could bring his last checker to safety. He could roll a big double. These threats are immediate so the position his highly volatile. Big advantage to black.

The rule of thumb is that if you are ahead in two of three elements then you should at least be considering doubling. It should be obvious from this that black has a powerhouse double.

Waiting until your opponent has a clear drop is not the way to maximise your equity at backgammon. You must double when you threaten to lose your market by the time it is your turn to roll again. You will lose some games in which you double – that is in the very nature of the game and what makes it such a great game in the first place. However, by doubling at the right moment, you will win lots more two-pointers and four-pointers (when you win a gammon).

Should white take? If white estimates he can win approximately one game in four then he should be taking. Most good players will be able to judge from experience that this is a take. A lot of the time when black hits, e.g. 52 played 15/8*, then white will have immediate return game-winning shots and in some cases he will win a gammon if he can hit and close out two of black’s checkers. It’s impossible to count all the hitting sequences but white will get a single shot (which he is 30% to hit) often enough to make this a comfortable take. Thus the position is both a correct double and a correct take as evidenced by the rollouts below.

Incidentally how would you play 32 as black after double/take? I hope you would play 7/5*, 6/3 despite the fact it leaves three blots. 6/4, 6/3 would be a huge error. 7/5*, 6/3 wins many more games and many more gammons than 6/4, 6/3. Yes you will occasionally lose a gammon by making this play but as we’ve said before you have to accept the downside in backgammon with equanimity. If you can’t cope with losing try something more sedate like tiddlywinks!

Chris Bray
03/2007

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