Accepted bidding theory of preempts

An accepted bidding theory is that preempts gain by preventing the opponents from conducting careful auctions. That may be true in the long run, but on a given deal, a preempt can impel the opponents to bid with all the more determination and end at a contract they wouldn’t have reached otherwise. And then the preempt may guide declarer’s play.

In a team match, one South opened one diamond after three passes, North responded one spade and South jumped to 2NT. North might have tried for slam in diamonds, but he knew his partnership had only 30 high-card points. So North raised to 3NT.

South had an ideal hand, and six diamonds would have been a good contract. West led a heart, and South eventually took 12 tricks with an end play. NorthSouth were relieved to see that with spades breaking badly and the king of clubs offside, six diamonds would probably fail.

In the replay, where West preempted with a cheesy weak two-bid, NorthSouth reached the slam on momentum. West led a spade, and South took dummy’s king and tried a club to his queen.

When the finesse lost, South seemed doomed. But after he won West’s trump return, he saw one chance: South led the queen of hearts. West’s king covered, and declarer took the ace, drew trumps, took the ace of clubs and ruffed his last club in dummy. He came to the ace of spades and took his last two trumps, pitching hearts from dummy.

East was “transfer squeezed.” Whether he threw his jack of hearts or unguarded his jack of spades, South would get his 12th trick.