Just about everyone has played the childrens game of tic-tac-toe, in which the only realistic hope of winning is to pose a dual threat; that is, to create two potentially winning boxes, so your opponent can block only one. (Of course, as any tic-tac-toe master knows, this cannot be done by force; the game is a draw with best play.)
The principle of the dual threat is also paramount in bridge. As declarer it may not be feasible to make your contract with any single line of play; but if you have two possibilities, the defenders may not be able to block them both. The idea is to keep two (or more) options alive as long as possible; then, as soon as the defense leaves an opportunity, snatch the one that will work. Witness todays deal.
South and North both bid aggressively South with one spade, and North with his raise to game but the final contract was sound. Shy bidders take note! Aggressive bidding has proved to be a winning strategy, especially in tournament play.
West led the diamond king then shifted accurately to the spade jack, ducked to Souths king. Declarer has two potential ways to make his contract: Ruff a diamond in dummy, or establish dummys long heart into a winning trick. Unfortunately, neither of these can be executed outright. If declarer leads a diamond, East will play the ace and another trump; if declarer pursues hearts, he will end up an entry short.
The solution is to retain flexibility; declarer must not commit to one option or the other immediately. The play to keep both chances alive is to lead a heart to the ace, ruff a heart high (South must save the deuce) and exit with a diamond. East wins but finds himself in a quandary to counter both threats.
If East plays the ace and another spade, South will unblock to win the third spade in dummy; then the fifth heart can be enjoyed using the remaining club entries. If East does not clear trumps, declarer will simply ruff a diamond after all.
© 1990 Richard Pavlicek