Two Blots

Two Blots
by Walter Trice – 5 September 2006

Wouldn’t it be nice if you could just move your checkers to where they would be most effective, without having to worry about getting a blot hit? Alas, most of the time backgammon cannot be played this way, and short-term safety ranks prominently among the tactical priorities.

Sometimes, though, positions come up in which caution may be set aside for the moment. It is important to recognize these opportunities and take advantage of them. One type is very simple and easy to spot: when your opponent has two blots in his home board, that’s a time to look for a positionally strong play. If you leave a blot and get hit it is unlikely that your opponent will be able to clean up both his home board blots. It will be legally impossible, unless he rolls doubles, for him to hit and clean up both his home board and his outfield. Thus by hitting he may be taking on a greater risk than you did in leaving him a shot.

Problem 1 is a typical example:

Red has a nice lead in the race, and he would like to just clear his outfield points, get his checkers home, and bear off. This is not so easy to do here without leaving a shot for White at some point. Red could hope for a roll like 5-5 or 4-4, or he could hope to outwait White, but chances are that if he plays as safe as he can he will wind up leaving a shot for White anyway.

At the moment, though, White has two blots in his board, while Red’s board is blot-free and four points strong. This is Red’s big chance to do as much of the clearing work as he can in one roll. The best play of Red’s 4-3 roll is 13/9, 13/10!

Note that Red clears the point that is directly blocked by two White points – the hardest to clear. If he gets away with this play then he should be able to get out of jeopardy by leaving at most one single direct shot later.

White could roll 2-2 or 3-3, making Red regret his boldness, but White’s next best roll, a 3-2, would leave him the underdog. After White’s 18/15*, 5/3, Red would actually have 16 return shots from the bar, even though none of them would be direct.

Problem 2

In Problem 2, Red has only a small lead in the race. Here White’s two home board blots would let him clear the lagging 16 point if that’s what he wanted to do. But White’s stripped outfield points mean that Red may be getting a shot soon himself, if he keeps the pressure on. The simple, relatively safe 11/8, 4/3 is perfectly reasonable, but Red can also use his temporary immunity to shift points in the outfield with 13/10, 11/10, leaving White a double shot. The point of this play is that it will make Red’s life easier if nothing special happens in the next few rolls. The blot on the midpoint can get home or to safety on the 10 most of the time, and the 10 can often be cleared safely if necessary. In this way Red gives himself more flexibility, and more time to play safely without damaging his home board.

Problem 3

Problem 3 is a follow-up to #2, after Red makes the unimaginative play, White rolls 6-2, and then Red gets a 4-3. White’s home board blots are still there. After White has cleared his midpoint and given himself some playable spare checkers for timing, Red’s 16 point has become a liability. Hence he should take the “two-blot opportunity” to clear it with 16/13, 16/12, a play that would be much too risky if White did not have the home board blots.

Problem 4

Red is up 24 pips, but the men on White’s bar point have miles to go before they sleep. With two blots in White’s board and a handy 6-5 roll, now is the time for the first of them to make his run (18/7). This is the best play to simply win the game, but the rollout shows that it also pays off significantly by cutting down Red’s chance to lose a gammon! The way to get gammoned from this position is to wait until White has strengthened his board, play safe until you run out of sixes and are forced to break the 18, and then get both men closed out.

Problem 5

Moving 18/7 would have been suicidal in Problem 4 if White’s board had been stronger. Here we see that two blots in Red’s board can reduce the opportunity represented by two blots in White’s board. But Red does not have to wimp out completely and play the passive 8/2, 8/3. Either of the plays that cover the ace point, leaving a blot exposed to a simple direct shot, is better. After all, White could roll a six leaving a blot for Red to shoot at, so improving Red’s own board is worth a small risk.

Problem 6

In our final example the opportunity represented by White’s two blots is easy to overlook, and in fact a very strong player made a routine play here.

The key is that Red is down 20 pips in the race, so he is motivated to try to keep White blocked. What Red can do with his 1-1 roll is to slot a fifth point in front of White’s anchor by playing 16/15(2), 11/9. With a bit of luck he’ll roll a six next time and cover it.

 

Here are the rollouts for the positions above:

Problem 1

Problem 2

Problem 3

Problem 4

Problem 5

Problem 6