Blue should keep building the prime. Blue trails by 7 pips, 146 to 139, but holds the 5, 6, 7 and 8 points with an anchor on White’s bar point, while White’s back checkers sit alone on Blue’s 2 and 4 points. Blue plays 13/9 13/7, bringing two builders down so that spares on the 9, 7 and 6 points all aim at the 4 point, where pointing on White’s blot would complete a five-point prime. The blot on the 9 point is exposed to 13 rolls, but White’s two-point inner board makes the hit cheap. Hitting with 8/2* 6/2 makes a point too deep to block anything and breaks the 8 point, so the prime shrinks to three blocking points. It loses 0.066 equity, an ERROR. Running with 18/8 abandons the anchor and loses 0.042 equity, an ERROR.

Blue should anchor first and prime second. Blue holds the 5, 6, 7 and 8 points, White holds the 17, 18 and 19 points, and the race is nearly level at 152 to 148. White’s spares on the 17 and 18 points aim at the 20 and 21 points, where a new point would trap Blue’s two back checkers, while White’s own back checkers sit as blots on Blue’s 1 and 3 points. Blue plays Bar/21 24/21, entering and making White’s 4 point in one move. Blue’s back checkers stop being targets, and Blue can wait for White’s blots to run into the four blocking points. Hitting loose with Bar/21 6/3* leaves blots on the 3, 21 and 24 points, and 17 rolls hit the 3 point, any 3 from the bar or a 2 from the 1 point. It loses 0.129 equity, a BLUNDER.

Blue should keep priming rather than protect the lead. Blue leads by 37 pips, 124 to 161, and holds the 6, 7, 8, 9 and 10 points, while White holds anchors on Blue’s 5 and 2 points behind a three-point inner board. Blue’s three spares on the 6 point can only work on the 4 point, and the two checkers on the 13 point are Blue’s last timing. Blue plays 13/9 6/4, slotting the 4 point behind the prime and adding a builder to the 9 point. Only 12 rolls hit the slot, and a hit costs little against three points. When White misses, Blue covers from the 6, 8, 9 or 10 points, and six blocking points then surround White’s anchors. Playing safe with 13/7 stacks a fourth checker on the bar point, blocking nothing new, and spends a roll of timing. It loses 0.021 equity, an ERROR.

Blue’s plan is to escape now and outlast White’s back game. Blue leads by 70 pips, 166 to 236, and holds the 6, 7, 8 and 9 points, while White has eight checkers back on Blue’s 3, 4 and 5 points and one made inner board point. Blue plays 24/15, bringing the last back checker out while a hit costs almost nothing, because Blue re-enters at once against a one-point board. Left on the 24 point, that checker would have to run later, alone, past White’s spares on the 10 and 12 points against a stronger board. Blue wins a gammon in nearly 30 percent of games, the usual price of a back game with too many checkers back. Making the 11 point with 16/11 13/9 builds a fifth blocking point but leaves the back checker where it stands. It loses 0.065 equity, an ERROR.

This is a priming battle, and Blue’s back checkers must move before Blue’s timing is gone. Blue holds the 5, 6, 7, 8 and 9 points with three White checkers trapped on Blue’s 3 point, while White holds the 18, 19, 20 and 21 points in front of Blue’s two checkers on the 24 point. Blue has only three spares, so rolls wasted inside the board soon break the prime. Blue plays 24/23 24/22, bringing both back checkers to the edge of White’s prime, where a 5 or a 6 next turn escapes or hits White’s blot on the 17 point. Playing 24/22 6/5 wastes the 1 on a spare and leaves a lone checker on the 24 point that only a 1 or a 2 can move. It loses 0.096 equity, a BLUNDER.

The prime is already doing its work, so Blue’s job is to free the back checkers. Blue leads by 25 pips, 138 to 163, and holds the 5, 6, 7, 8 and 9 points with three White blots stuck behind them on Blue’s 2, 3 and 4 points, while White’s spares on the 12, 13 and 14 points are ready to make the 18 point. Blue plays Bar/23 24/18, entering and stepping straight onto White’s bar point before White can build it. White hits there often, but a hit against White’s three-point inner board costs Blue little, and every roll White spends on Blue’s back checkers leaves the three blots under the prime. Hitting with Bar/23 8/2* attacks a checker that is going nowhere anyway and leaves a blot on the 2 point that 12 rolls hit from the bar. It loses 0.026 equity, an ERROR.

Blue should get the back checkers moving while White’s blocking points still have a gap. Blue holds the 4, 5, 6 and 7 points against White’s blots on Blue’s 1 and 3 points and trails by 11 pips, 157 to 146. White holds the 16, 17, 19 and 20 points, but the 18 point, White’s bar point, is still open and White’s inner board has only two points. Blue plays 24/18, planting a checker on that bar point. White can hit with a 1, a 2 or a 6, but the hit costs Blue little against a two-point board and leaves White’s builders exposed to return shots. If White instead makes the 18 point, Blue’s checkers on the 24 point sit behind a five-point prime. Bringing a builder down with 13/7 is safe but leaves both back checkers waiting for exactly that. It loses 0.058 equity, an ERROR.

Blue should hit, because the prime turns a loose hit into a trap. Blue trails by 29 pips, 165 to 136, with four checkers back, but Blue holds the 3, 4, 5 and 6 points and White’s two back checkers on Blue’s 1 point are already behind them. Blue plays Bar/22 13/11*, entering and sending a third White checker to the bar. White enters only with a 1 or a 2, 20 rolls of 36, and the blot on the 11 point cannot be hit this turn because White must enter before anything else moves. With three checkers behind four blocking points, White’s 29-pip lead means little. Making the anchor with Bar/22 24/22 is solid but lets White cover the blot on the 11 point and start bringing the lead home. It loses 0.170 equity, a BLUNDER.

Blue’s back checker cannot wait. Blue trails by 25 pips, 123 to 98, so the prime is Blue’s game, and Blue holds the 3, 5, 6, 7 and 8 points against White’s last checker on Blue’s 2 point. The danger is the three White spares on the 17 point, which aim at the 21 point and would leave the checker on the 23 point with only a 5 to escape. Blue plays 23/21 13/10, making the 10 point and stepping up to White’s 4 point, where 3s, 5s and 6s escape next turn and a 9 hits White’s blot on the 12 point. White can hit on the 21 point, but a hit from the 19 or 20 point breaks White’s board. Making the same point with 13/11 13/10 leaves the back checker where White wants it. It loses 0.036 equity, an ERROR.

Blue’s plan is to trap White’s last checker, not to race. Blue trails by 26 pips, 117 to 91, but holds the 4, 5, 6, 7 and 8 points with spares on the 6, 7 and 8 points and an anchor on White’s bar point, while White’s last checker sits on Blue’s 1 point. Blue plays 8/2 7/4, slotting the 2 point right in front of that checker. Only a 1 hits, 11 rolls of 36, and when White misses Blue covers with any 2 or 4 from the new spares on the 4 and 6 points, leaving White’s checker facing six blocking points. If the slot is hit, the anchor on White’s bar point keeps Blue in the game against White’s five-point board. Running with 18/9 gives up that anchor and leaves two blots while the trap stays open. It loses 0.121 equity, a BLUNDER.