In the linked document, I have posted 5 positions that arose during the same endgame. In the first position, Blue has borne off all but two checkers and has a 95% chance of winning. In the second position, Blue’s winning chance has fallen to 87% (because Blue no longer has a point?) In Positions 3 - 5, Blue’s winning chance has fallen to the 46% - 55% range, presumably because White has built a prime.

I have a number of somewhat general questions about these positions:

Q1: In the first position, what should each player’s game plan be? Of course, Blue wants to get home — does this usually require making a point or trying to run one checker home by itself? Presumably, White wants to build a prime — but does it matter much where White builds her prime?

Q2: By the time we reach Position 3, how do the game plans change? I assume that White should break her 6-prime to force Blue to break her point. But which point in the 6-prime should she break?

Q3: When we move from Position 4 to 5, Blue’s win chance goes from 46% to 55%. Why is this? The positions look very similar to me.

I also have some questions about XG’s recommendations (which strike me as very strange):

Q4: In Position 2, White’s play makes a 3 prime (by making the 10 point) whereas XG breaks the prime entirely. What is XG doing here?

Q5: In Position 3, I would have played Bar/19 9/7. The idea is to break the prime and so force Blue to play 1s (aiming for the close out). However, this doesn’t even show up in XG’s list so must be a huge blunder. What’s wrong with my play? In addition, why is XG’s play so much better than the play White chose (Bar/17)?

Q6: In Position 4, both White and XG played the same 6 (from the 19 point). However, apparently it makes a huge difference how you play the 1. Why?

Q7: In Position 5, I would have again broken the 6-prime, e.g. by playing 9/6 7/6. Again, however, this is a huge blunder. So what I am missing? And what was my opponent White missing when they made their play?

I know this is a lot of questions — so feel free just to answer one or two of them! And thanks in advance for any ideas or suggestions.

One thing I should add -- in all of these positions, Blue is leading 1 away/2 away and we are at Crawford. So Blue doesn't care about gammons (they just need one point win). Also, White can't win a gammon since Blue has already borne off checkers. As a result, I think that gammons are irrelevant here.

You shouldn't put any stock in XG's analysis, it doesn't understand this type of position.

The most important thing to understand happened earlier in the game -- Blue should have not have hit so many checkers. I've literally never been forced to be in a position where my opponent has all his checkers available to roll an outside prime around like this.

Position 1 It does seem like Blue gives White the most headaches by making a point.

Position 3 I'd break the 9 point so as not to let one checker get home. Though it's much easier to roll the prime forward against 1 checker than 2, so I guess it could be right to let one checker escape, roll the prime forward a bit more, then go back for the second checker. But with no other Blue checkers on the board, it so important to close out both, that I'd be worried that I wouldn't get a chance to hit that second checker again.

Thanks for the comments. Do you have a sense of Blue's winning chances in this kind of position? (I believe that, even if both of Blue's checkers are closed out, Blue should still have something like 35%.)

I don't have a great handle on it. I know it's pretty easy to roll an outside prime forward against one checker if you have all 15 checkers to work with. So in that case you're over 90% to close out one checker with perfect play, but needing to contain and close out 2 checkers seems a lot trickier.