The objective of the person playing the backgame is to hold both the points in his opponent’s board and at the same time use their remaining checkers to build a strong home board. If the back game is well timed the opponent will be forced into leaving a blot, probably exposed to a double shot. The idea being that the player of the backgame then hits the shot and contains the hit checker.
As the player of the backgame will normally be in posession of the doubling cube the final fase is to win the game with a well-timed redouble.
The first piece of advice about backgames is this – try to avoid them unless absolutely necessary. They are great when they work but they are difficult to play and when they go wrong you will quite often lose a gammon. No matter how well you play one bad roll can destroy even the best timed backgame. Look at the position above and see what would have happened if black had rolled double 4 – his beautiful home board would have been ruined completely.
However, black has a 51 to play and must choose between (a) 23/18, 8/7 and (b) 8/2 (I hope no-one considered playing 21/15??). Which shall it be?
The game has reached its climax and the next two turns (one by each player) could be decisive. (a) guarantees black’s timing by freeing the spare man from the rearmost point whilst (b) makes a strong home board but does risk some bad numbers (such as 44 and having to run off the 21-pt with any 6) next turn. Are we any clearer?
Having looked at the general considerations what about specifics? If black plays (a) then nearly all of white’s 1’s play much better than after (b). The second consideration is that after (a) and a subsequent hit by black, black’s home board will not be as strong as after (a) and white may be able to return hit from the bar.
These specific considerations outweigh the generalities (often the case in late game positions) and (b) is correct as can be seen from the rollout below. In the game black chose (a) and white responded with 41, played 8/7*/3. Black fanned, white never left a shot in the bear-off and easily won a gammon.