South dealer, North-South vulnerable.
Only rarely does declarer choose a game or slam contract based on a 4-3 trump fit. This is as it should be, since a contract where he has only seven trumps to the opponents six is not the type of trump superiority one yearns for in life. There is an inbred danger of losing control of the trump suit and going down to defeat. Normally such contracts are avoided by finding a longer trump suit or by playing in notrump.
However, there are times when there is no better alternative than to choose the 4-3 trump contract — as in the present case.
Opening lead — king of spades.
Contracts that are based on a 4-3 fit often require careful handling to compensate for the trump deficiency, and this was where South fell from grace.
West started with the K-A of spades and continued with the queen. South ruffed, played three rounds of trumps and when the suit proved to be divided 4-2, instead of 3-3, began to play diamonds. West ruffed the third diamond with his remaining trump and cashed the 10-2 of spades to defeat the contract two tricks.
In effect, declarer miscued when he trumped the third round of spades. By doing so, he put himself in a position where anything but a 3-3 heart division would endanger the contract. Instead, South should have discarded a club on the third spade, thus retaining full command if the trumps were divided either 3-3 or 4-2.
No return by West could then have hurt declarer. Another spade would be trumped high in dummy as South retained all four trumps in his hand, while a diamond, club or heart return would allow him to draw trumps and collect the ten tricks he had started with.