Prime vs. Prime
Hello dear backgammon fans! This is Marc Olsen. In this blog post, we're going to look at a specific type of position which we call "prime versus prime" or a “priming battle”. Look at the position below:
Prime vs. prime position
A prime versus prime position is essentially a middle game because both players still have back checkers. So, neither of them has achieved full freedom yet due to the back checkers. One essential characteristic that identifies a prime versus prime position is that both players are aiming for the prime game plan. In the picture above, you can see that Blue has a prime trapping two checkers; and White also has a prime trapping two checkers.
The first thing that matters in a prime versus prime is the structure: Whoever has the stronger structure has an advantage. Let's look at the structure in this case (same as the picture above).
Blue has a pure five prime; so does White. You could say the structure there is actually the same. However, how is the structure doing priming-wise?
White’s five prime is blocking Blue’s anchor, which is on the edge of the prime. Since those checkers are on the edge, they have daylight. They can jump out directly with a six. However, that's not the case in Blue’s five prime. The two checkers of White don't have daylight with a single move. So, these two checkers are getting primed way better than Blue’s anchor. That's a big advantage here for Blue.
The next thing we have to consider in a prime versus prime is the timing. So what is timing? (see also; our blog post about timing)
Timing is the flow of the game and the indicator of how strong your position will be when you reach the crucial moment in the game. The crucial moment in the game in a prime versus prime is typically when one player crunches his prime involuntarily. Whoever crunches his prime first will probably lose the game in a prime versus prime position. So, the better timing you have, the longer you can hold your position. The worse timing you have, the fewer moves you've got until your position collapses.
Let's look at the same position again:
Blue has way better timing than White because Blue can move his checkers from the midpoint- a good supply of spare checkers. He can move them with a couple of rolls and still hold his structure while White doesn't have any spare checkers except for the one in his five point. So, you can see that White’s being ahead in the race in this position is actually a disadvantage in terms of timing. In a prime versus prime position, you want to have superior timing. Therefore, it's usually an advantage to be down in the race, instead of being ahead. This is kind of opposite to the usual backgammon position.
We can also see that the two checkers of White, buried behind blue's anchor are really hurting White's position because they are not performing any useful duty for the time being. Because they're behind the anchor, White would prefer to have them out here to form a six prime:
Or, even up here:
to have more timing because if they were there, White could also move several turns before he had to crunch his five prime. But as it is now, he cannot. He has to give up his prime next time, which will allow Blue to escape and still keep White primed. White’s having to let go of his prime would be the crucial moment in this prime versus prime game. For instance, like this:
He still has a four prime, so it is not over yet. But, it was a crucial moment because now he lost a lot of his prime value, and Blue can easily escape. Now it's not only the sixes but also the fives that get him to jump the prime, and the battle is essentially lost here for White. Blue should double, and White can't even take.
If we were to give White a little bit better timing, like the one below:
So here, White has more than enough timing to take the cube.
Let’s also improve Blue's position a little bit as well. Every pip we move backward is actually an improvement for blue. For instance, this position is even better for blue, even though we just lost three pips:
The blot there; we should call it a slot because it's slotting like a slot machine to the point we want to make. In this case, it is slotting for the six prime. If Blue rolls a four, he can make a six prime—the strongest structure in backgammon. So, we've got structure.
Before we finish up, let’s talk about strong structure. What is it?
A strong structure is a pure structure, a structure with no gaps. And, it's an efficient structure; namely, a structure that utilizes the checkers to the maximum. For instance, this structure here is very efficient:
We've got eleven checkers. Ten of them form the five prime, and one is a useful spare checker - that's efficient. So, purity and efficiency are definitely very important as well.
To sum up, the two key points to manage a prime versus prime position (a.k.a. priming battle) is:
To have good timing (so usually you want to be down in the race) and,
To have better structure.
See you in the next blog post, and have good luck in your game!
You can see the full video here!