Mandatory falsecards may temporarily mislead partner, but the trade-off of confusing partner as opposed to declarer is one you can accept if the circumstances are right.

In today’s deal, South exploited the vulnerability with an aggressive four-spade opening. He had good spades, no defense and a singleton in the other major, making this a reasonable tactical move.

A minor-suit lead would have given the contract no chance, but West led a top heart, of course. On seeing the dummy and a discouraging card from his partner, West shifted to a diamond. Declarer took dummy’s ace and threw a diamond on the heart queen, setting up a trick in that suit.

Declarer ruffed the next diamond, crossed to the club ace and led a trump off dummy. When East followed low, declarer won his king. He needed to bring spades in for one loser, and if West had instinctively followed with the five, South would have had to play for ace-doubleton on his right by leading a low trump next, making his game.

However, West was aware of the situation and dropped the 10, creating a losing option for declarer where none had previously existed. South now had to decide whether West had jack-10 doubleton or jack-10-low. The Principle of Restricted Choice could not help because West had two equals either way. The only inference he had was that West might not have found this defense if he had three trumps. So South continued with the spade queen and lost his game.

Despite the disparity in North’s suits, he preferred to get his hand off his chest in one turn, hence his Michaels Cue-bid as opposed to a simple one-spade overcall. South jumped to four hearts, and West tabled the diamond queen.

With a club trick to lose, South needed to limit his trump losers to two. He won the diamond king in dummy and called for a low heart. If East followed with the nine, declarer intended to follow small. Since West had opened the bidding and had not led a top club, he seemed to have at most eight points in the minors and thus had to hold a top heart honor. Intended to duck the first heart would be beneficial if West held a singleton top heart honor, and it would almost never lose against other lines.

However, East had also been thinking ahead and had worked out that declarer must have the diamond ace, and that even if West had the spade king, it would be in the pocket. Since the defenders were entitled to at most one club trick, they needed three trumps — which could only be done if West had the heart ace. That would be simple if West had the doubleton ace, but what if it were singleton?

Hoping to put declarer off the right track, East inserted the heart jack. Now declarer could no longer duck in complete safety, since West might have aceking-nine. No count of the hand was available, and declarer was forced to guess. Can you blame him for putting up the queen and dooming his own contract?

This week’s theme involves giving your opponents a chance to go wrong. If a play has only upsides, it is clearly a useful weapon to add to your armory.

A normal auction from a teams game landed South in a poor but makeable contract on today’s deal. Not for the first time, though, the defense had other ideas, and they successfully led declarer down the garden path.

West led his fourth-highest spade against three no-trump, and declarer optimistically tried the 10, covered by the jack and ace. Needing four club tricks for his contract, declarer laid down the club ace, hoping to guess well on the next round.

When East followed with the deuce, declarer had to decide whether West had king-third or jack-third. He mentally flipped a coin and called for dummy’s 10, landing his game.

In the other room, East made declarer’s losing option more attractive by dropping the club nine under the ace, making dummy’s spot cards solid. Thus, declarer could now succeed against one 4-2 break as well — jack-nine doubleton with East. This extra chance was enough to tip the scales in favor of playing the club queen. East had swindled declarer out of his game bonus.

An interesting corollary to this is that if an expert East does not drop the nine, he cannot hold king-nine-low. However, jacknine-low is still a possibility because playing the nine from that holding would serve only to help declarer.

None of the falsecards discussed this week are likely to cost, and all of them offer declarer a different, unsuccessful line of play. Here, West led the unbid suit against four hearts, setting up a spade winner for his side and compelling declarer to bring trumps in for one loser.

Some would tackle trumps by leading to the queen, intending to finesse the 10 on the way back if that loses. However, due to South’s poor intermediates, he preferred to cash the ace, then play toward the queen. In comparison to the other line, this picks up a singleton jack or king offside and the doubleton jack with West, five cases in total. The alternative line succeeds against king-jack-low and jack-nine doubleton offside, only four cases.

Had East dropped the nine under the ace, South would no doubt have led to the queen next, since he could not succeed against king-jack-fourth with West. But our East was made of sterner stuff and nonchalantly dropped the heart jack under the ace, presenting South with an attractive losing option.

Taken in by this, declarer confidently finessed the heart eight on the next round, playing for East to have started with the bare jack or king-jack doubleton. He could survive a 4-1 trump break, since dummy’s spade nine would serve to stop that suit and prevent the force.

Unfortunately for declarer, East won with the heart nine, and yet another apparently unbreakable game had vanished down the drain.

This week’s themed deals are based on mandatory falsecards in defense. When it cannot deceive partner, or if doing so will not matter, it may pay to try to lead declarer astray.

South somewhat prematurely committed to six spades instead of six diamonds here; then he had to make it. Having taken the heart lead in dummy, he focused on bringing the trumps in for one loser. There would be no problem on a 3-2 break, so declarer turned his mind to the possibility of a 4-1 split.

The percentage play here is simply to finesse the jack, gaining against the four cases of queenfourth onside compared with the one instance of a bare queen offside. This is what declarer would have done if West had followed lazily with the two. But West tried the effect of contributing the 10 at his first turn, offering declarer an alternative.

Seeing that he could now protect a singleton 10 to his left, declarer rose with the ace and returned the jack — and was mightily discomfited when East showed out.

South was just a little naive here. When the spade 10 or nine appeared, rising with the spade ace was playing against the odds. And note that South had an extra chance even if he finessed into East’s four-card suit. After a club return, declarer would win in hand, cross to the trump ace and diamond king to ruff hearts, then try to run the diamonds. If East had been forced to follow to three diamond leads, declarer would have finished in dummy at trick 12 for a trump coup.

In a high-level teams game, both tables reached four hearts on the lead of the club three. Both declarers played low from dummy, and East inserted the club 10. Each declarer won the first trick in hand and guessed well to lead a low trump. After winning the ace, both Wests continued clubs to dummy’s jack and East’s king. The defenders continued the accurate play by cashing the spade ace, then forcing dummy with a club.

At the first table, declarer ruffed low, then drew trumps with the jack, king and ace. After cashing the spade king-queen, declarer took a diamond finesse; when that held, he called for the diamond ace. When East discarded a spade, declarer had to concede the setting trick to the diamond king.

The second declarer, warned by the premature appearance of the trump ace, ruffed the third round of clubs with the heart nine and continued with the trump jack. He realized that the contract would depend on West holding the diamond king, and that entries to hand were at a premium, so when East followed with a low trump, declarer overtook dummy’s jack with his queen. Now he was in the right hand to take the diamond finesse. Once that succeeded, declarer led dummy’s trump four to his eight.

After drawing the last trump, declarer cashed his spade winners, then led a diamond to the 10 and jack. The diamond ace was his 10th trick: he had made two spades, three trumps, three diamonds, a club and a club ruff.

After West’s weak jump overcall, North’s cue-bid of three spades promised a game-going hand with at least three hearts. Despite South’s discouraging signoff in game, North continued rather optimistically to what proved to be the delicate slam.

West led the spade king to dummy’s ace, and declarer paused to form a plan. Declarer saw that even if trumps were 3-2, he would only have 11 top tricks. He rejected the idea of ruffing a spade low in dummy as hopeless, and saw that a squeeze on West between spades and a minor suit was impractical because of his need to find trumps breaking.

With known spade length to his left, declarer realized that pressure on East was possible but the key would come from scoring all his small trumps in hand. So he continued by cashing the two top hearts in his hand, followed by the club aceking. After ruffing a club, declarer returned to dummy with the diamond queen to ruff the fourth round of clubs. Declarer next cashed the diamond aceking, then led the fourth diamond from table. When East followed suit, declarer ruffed with his last trump.

At this point, declarer had taken one spade, two trumps, three ruffs and the five minor-suit winners, with the master trump still in dummy.

This line needed West to have either one or two trumps and East to have at least four cards in each minor. If that was not so, East could ruff a minor-suit card and leave declarer with a spade loser.

Eric Greco won player of the year for the ACBL by virtue of a series of outstanding finishes in the major events in 2018. I first registered Eric’s talent when he played for the U.S. Juniors over 20 years ago; here he is at work from the finals of the 1997 World Junior Team Championships. It was somewhat ironic that he found one of the best plays of the tournament here, to hold his losses on the deal to 5 IMPs.

In four spades on the opening lead of the heart 10, Greco rose with the king and ran the diamond 10. He won the heart return in dummy, and then passed the diamond nine after a lot of thought.

His plan was to set up the diamonds without letting East in. That would work if hearts were 5-2, but if hearts broke 4-3, there might easily be a trump promotion on the 13th heart.

All was well, since Greco had read the cards correctly, and West had no heart to lead when he took the second diamond. West exited with a club, and declarer ruffed, cashed the top spades and led the fourth diamond to pitch the heart loser to make the hand. Alas for USA, four spades doubled was let through in the other room when the first three tricks started the same way, but declarer then came to hand with a top spade to lead the diamond ace. West forgot to unblock his other top diamond on this trick, so East could not get in to cash the hearts, and the play transposed back to Greco’s line.

After some aggressive bidding from almost everybody at the table, West led a top spade against five clubs and shifted to a heart. When East won and returned the suit, South saw that it would be suicidal to try for a heart ruff in dummy, since West was all but certain to ruff in ahead of dummy. So declarer banged down the club ace-king and breathed a sigh of relief when the suit split.

Since his heart seven was surely going to be a menace against East, declarer could see that both opponents were going to be squeezed dry on the run of the trumps. West was in sole possession of the spade guard, so who would be able to hold onto the diamond guard?

On the last club, everyone came down to three cards. West had to keep the spade ace and reduced himself to two diamonds. When dummy let go of the spade queen from the board, East came under the gun. He had to allow declarer his game-going trick by unguarding one of the red suits.

Hard as it may seem, West could have attacked the entry to the double menace by shifting to diamonds at trick two, or East could have broken up the timing for the squeeze by ducking the first heart.

I suppose East might have figured out that even if South had four hearts, the heart losers were going nowhere. And if declarer held the diamond ace-queen, they would have to be doubleton. So, ducking the first heart must be right, hard as that might seem.