Here is a nifty defensive convention that I recently taught in my defense class that, as irony would have it, popped up in a recent over-under game at the club.
I am sitting East (well, actually I was sitting in the “Over” position in the North hand, but I rotated the hands for ease of viewing). We are vulnerable; opponents are not. The opponents reach 2♥ after the following unrevealing auction.
Partner led the ♦A and the weak dummy to my right came down. After dummy follows, what should I play?
A nifty defensive convention holding the QJ(xx) in a side suit when partner leads the Ace against a trump contract is to play the Queen under the Ace. This odd play of the Queen promises the Jack (or a singleton Queen), and is intended to suggest to partner that she may underlead her presumed King to reach your hand with the Jack if doing so might be advantageous to the defense.
I did that here, playing the Queen. Unfortunately, we had not yet reached that lesson in my defense class that my partner was taking, and so he did not make the diamond underlead. Had he done so, it would have led to a one-trick set, as all four hands were as follows:
With the immediate underlead, I would have gotten in with the ♦J and would have fearlessly shifted to the ♥K and and another heart. Partner would have drawn all of dummy’s trumps and the would have cashed the ♦K, for a one-trick set. Instead, partner made the small mistake of cashing another diamond; then he cashed the ♥A and led another heart. This permitted declarer to make three hearts for +140, since declarer only lost two heart tricks and was still able to get the diamond ruff.
While this convention does not come up every day, it comes up often enough so that it useful to remember it. When it works, the results can be devastatingly effective for the defense. And note that simply playing an encouraging signal on the lead of the Ace does not do the trick — partner would also encourage with a doubleton. How embarrassing would that be to underlead your King and declarer to take his queen-in-waiting, with your partner never getting her ruff with a doubleton!
Moreover, note that this convention only applies to trump contracts. This follows from the fact that partner would never encourage with a doubleton when defending a no-trump contract, since she will never want a ruff. Accordingly, an encouraging signal given in response to an ace lead in a no-trump contract means that partner has a high honor (or perhaps extra length) in the suit. In this situation, it would indeed be risky to unnecessarily unblock the Queen, as it may promote declarer’s 10 or 9.
This convention is not flawless however. I always discourage my partners from leading unsupported aces, but I’m sure the day will come when he leads the Ace without the King, with me holding QJxx and declarer holding K10x. Now partner’s Ace lead has already promoted declarer’s King and my play of the Queen under the Ace will promote declarer’s ten as well! But this possible scenario is not enough to discourage use of this convention. If this bridge nightmare happens to you, the remedy is to have a good laugh and move to the next hand.
A note on the bidding: the “under” player in the South hand made the very good bid of opening her skimpy 11-count. While saner people in the Charlotte bridge community would be aghast at this, I (and I believe Julie) would not hesitate to open this hand, particularly given the favorable vulnerability. My partner did not have quite enough to make a vulnerable takeout double with his so-so 13 count and terrible shape, and I did not dare come in with a 3♦ bid or a take-out double with such soft values. So even if we had defended perfectly and set the hand, we would have only gotten a slightly below average on the board, since East-West pairs that did not have to confront that pesky 1♥ opening bid found their way into an impregnable no-trump contract, making at least 2. In bridge, as in many endeavors, fortune favors the brave.
— Tom Hunt