Play the card known to be held

Mark Twain said of Rudyard Kipling, “Between us, we cover all knowledge; he knows all that can be known, and I know the rest.”

That would be a tough twosome to take on in a general knowledge quiz. In a bridge setting, though, it can be important to play the card that you are known to hold. How does that apply in this four-spade contract?

West led the club 10: jack, ace, eight.

After East shifted to the heart eight, what did declarer do?

North’s two-diamond response was natural and game-forcing.

With a diamond to lose, South could afford to concede only one trump trick. The initial plan was to hope that East started with royal10-third or any beneficial doubleton. Declarer would expect to play first low to his nine, then low to the jack.

So, South won with dummy’s heart ace and played a spade to his nine, losing to West’s queen. Now West led another heart. Declarer won and played a diamond to the queen and ace. After winning East’s diamond return on the board, South called for dummy’s second spade. What happened then?

Declarer was getting ready to play his jack, but

East followed suit with the four. Just in time, South hit the brakes. What was the spade position? East could not have started with K-10-2. If he had K-10-4-2, the contract was unmakable. But if he had 10-4-2 ... Declarer put up his ace to bring down West’s king and make his contract.

East should have played the spade 10 on dummy’s seven, the card he was known to hold from the first round of the suit.