One of the most difficult decisions as a defender is to know when to switch the point of attack when your opening lead appears to have been successful. Take this hand, from the 2008 European Championships match between Iceland and Norway.

In response to his partner’s overcall, West, Norway’s Terje Aa, led a heart and declarer, Sverrir Armansson, correctly allowed Jorgen Molberg’s nine to hold, expecting the suit to be divided 5-2 or 6-1. Had East continued hearts, declarer would have prevailed. So long as East held no more than one club honor, Armannsson would have had time to set up two club tricks. Although East could establish his hearts, he wouldn’t have the entry to enjoy them.

But Molberg found the killing switch to a spade. With a heart trick in the bag, the defenders were able to establish two spade tricks before declarer could set up his clubs.

In the other room Norway’s Geir Helgemo, North, opened one no-trump and East did not overcall. After a Stayman sequence, North ended in three no-trump and East led the heart queen. Without an overcall to warn him, declarer had no indication that hearts divided 5-2. The most likely heart division was 4-3, so the odds favored winning the first trick rather than ducking and risking a spade switch. But luck was with Helgemo. When declarer led a low club from dummy, West did not work out to fly with his king, and East won the trick (yes, ducking would have been better), allowing declarer to prevail.

To be third in hand at favorable vulnerability after two passes is a delightful position. You know that your left-hand opponent has a good hand so you can make life as difficult for him as you dare.

Here West had a good club suit and virtually no defense, so he opted for the three-level pre-empt, which worked very well. North’s takeout double was clear and South was happy enough to bid his reasonable five-card diamond suit. That ended the auction.

After cashing two rounds of clubs, West had to decide what to do next and he found a good play, the opportunity for which crops up quite frequently if you are on the lookout for it. He switched to the spade THREE.

Declarer won with the ace and no longer had a winning line. As soon as East got in with a red-suit trick, he could play another spade, establishing his own queen, which he could cash when he was next on lead.

Declarer now cashed the diamond ace and played hearts. East took his ace and led a second spade. Declarer won and continued with hearts, hoping that East had four hearts and three diamonds, but West ruffed with his diamond seven, and three diamonds went down a trick.

Note that if West had switched to the spade jack, that would have sunk the defense, for East would not have been able to continue the suit when he got in.

When the opponents pre-empt, you are often forced to guess, as in today’s deal. But how unreasonable is it to bid slam here, hoping for the spade queen or spade length in dummy?

The defenders lead the heart queen to your ace. You cash the spade ace and your worst fears are realized when West discards on this trick. What should be your plan next?

You must now strip all the clubs from the hand that has the diamond ace. If East has only two clubs, you need to decide which defender has the diamond ace, but why not cash two clubs to see if you can find out more? Best is to lead the club queen first. After all, West may give you honest count if he thinks his partner needs to know when to take his club winner.

When you cash a second top club, you discover the club break, so it is quite safe to take just one of your remaining club winners (not both!), then lead a diamond. You need West to have the diamond ace — if East had it, he could exit with his last club. When West wins and plays a red suit, you win in dummy, pitching your club from hand and take the spade finesse.

Note that had you cashed your last club before leading your diamond, whoever wins the diamond ace can play a second diamond and force you to ruff in hand, preventing you from taking the spade finesse.

Second hand low is not always best. Consider today's deal from the 2011 Bermuda Bowl, where South generally ended up playing two or three no-trump on a club lead to his nine. All declarers next played the diamond king, and most Easts won the second diamond to return a club. South does best to win and lead a spade, hoping to force an entry to dummy's diamonds.

West should now infer that East must have the spade king to have won the diamond. So if South leads a low spade, West must insert the 10! Now the defenders can deny declarer an entry to dummy whatever he does. By contrast, if South starts by leading out the spade jack, both defenders must duck.

When Chris Bosenberg of South Africa was declarer, he played on diamonds at trick two, and East took the second diamond and played back a heart.

Declarer finessed, cashed the club ace, and exited with a low heart — a fine play. East won and returned a low heart, letting declarer repeat the finesse (West pitching his diamond and a club) and play a spade to the nine and king. That now ensured the entry to dummy for the contract.

Here, the blocking play of the spade 10 by West would not have worked. East could win the spade king and return a spade, but declarer could play the spade jack. Now West’s winning the trick gives declarer the entry to dummy, while ducking the trick leads to West’s being subsequently endplayed in spades.

A vise squeeze conjures up images of the jaws tightening till something has to give. In England it is called a vice squeeze, which conjures up a completely different image.

You don’t recognize the maneuver? Well, Antonio Sementa demonstrated it nicely here in a deal from the 2011 Bermuda Bowl.

Whereas four hearts had gone down without a fight in the other room (declarer winning the first club, cashing the heart ace, and running into a trump promotion), Sementa ducked the first club, then led out the heart ace, and overtook the diamond jack with the diamond queen to play a second heart. East won the king and exited in diamonds.

Sementa won in hand, drew the outstanding trump, then tested diamonds, ruffing the fourth diamond back to hand. He had reached an ending where he had played four rounds of hearts, two clubs and four diamonds. He could simply have played for the spade ace to be onside now, but the auction had suggested this would not work.

Instead, Sementa led out the last trump. He was hoping to find the queen-jack of spades onside together with the club guard. And so it proved. On the last trump West had to pitch a spade, reducing to one honor and his master club, and now declarer led a spade up to the queen, king and ace, scoring trick 13 with the spade 10.

When the Open teams of England and Turkey met in the 2008 European Championships, Yalcin Atabey of Turkey had done well to reach five clubs as South. Those declarers who ended in three no-trump,whether North or South, were doomed to fail, as both East and West had natural red-suit leads.

In opposition were England’s Hackett twins, Justin and Jason, and Justin led a heart against the club game. At first glance there appear to be three losers — one in each of the red suits plus the spade ace. But with those excellent spade intermediates in dummy, the contract looks safe. Declarer will win the heart lead, enter dummy in trumps, and lead a spade to the king. West wins with the ace and leads a heart to East’s king. East does best to return a diamond. However, a spade to the queen and a spade ruff set up the suit. It only remains to finish drawing trump and discard two diamonds from hand on dummy’s spades.

Declarer began as prophesied. At trick three, Atabey led a spade to the king, which held, Justin ducking impassively. South continued with a spade to the 10. In with the jack, Jason returned a diamond, taken by dummy’s ace. Atabey drew the remaining trumps, then confidently led the spade queen, on which he discarded a diamond, believing that East held the ace. But it was West who produced this card, and his diamond return saw the game drift two down.

In today's deal you have bid to what looks like an excellent no-trump slam. North's jump to six may seem precipitous, but he has so many high cards that it would be pessimistic not to drive to slam.

Since you have nine tricks outside hearts, three tricks from that source will give you your contract. However, while it might appear that all you need to do is find one heart honor onside, you will need to exercise considerable care in managing your entries. Can you see why?

The point is that you may need to take three finesses in hearts, so you should arrange your play of the spade suit with this in mind. After winning the club lead, you play the spade king and overtake with the ace. The first heart finesse loses to West’s queen and you win the club return. You then lead the spade 10, overtaking with dummy’s queen when West follows low.

If spades break 3-2, you can afford this double overtake; the spade jack will draw West’s last spade. If instead East began with a singleton spade, you will have cleared the way for a finesse of dummy’s spade eight! Let’s say that East does indeed show out on the second spade. You take a second heart finesse, which wins, and return to dummy with a marked finesse of the spade eight. After cashing the spade jack and spade three, you finesse for the third time in hearts and mark up your slam.

Tim Bourke of Canberra, Australia, spotted this fine play in a delicate 4-3 fit from the Transnational Open Teams at the last world championships.

Against four spades West led the spade jack to the seven, two and king. At trick two, declarer played the heart nine around to East’s king. That player switched to the diamond five to his partner’s king, on which declarer unblocked the 10 from dummy.

Now West returned the spade six. To maintain trump control and to cater to a possible 4-2 trump break, declarer played the eight from dummy. South won with the nine and persevered with the three to dummy’s queen. Declarer cashed the spade ace to draw the last trump, then finessed in diamonds, cashed the diamond ace (dropping the jack), then played the diamond queen. The clubs provided the rest of the tricks, giving 620 to East-West.

It was impossible to see, but had East continued with a top spade at trick three, the combination of the bad lies in spades and diamonds would have been too much for declarer. Of course, the auction had given him no chance to get this right.

But declarer had deviated from the winning line, one that he really should have spotted. Declarer’s best play is to duck trick one! Now the defenders cannot do anything. Maybe a club shift would be best, attacking declarer’s communications, but so long as he plays diamonds for two tricks, one way or another he is home.

While a fair percentage of the North-South field reached four spades on this deal from a major pairs game, with mixed success, two spades was a sensible partscore.

The club six was often the lead from West, and declarer usually put up dummy’s king to muddy the waters. When East took the ace, he had the problem of whether to play for a ruff or to cash the hearts. It looked reasonable to return a club, and now declarer was in with a shout to make his game.

However, when he takes the club jack, he has to decide what to do next. Obviously, he has two potential winners in dummy for his heart losers. And indeed if diamonds are 3-3, he might emerge with 11 tricks, but if he plays for the diamond break, he might finish with only nine winners. For example, if he tests diamonds after cashing the top spades and the suit breaks 4-2, he might not get the club discard in time.

The best play is to enlist the opposition’s help by leading the diamond queen before cashing the spade ace-king. Both defenders can be expected to give honest count, perhaps each assuming their partner has the diamond ace. Now when the suit seems to be 3-3, declarer can cash the top spades, unblock the diamonds, and follow up with the club queen. When the same hand is long in both black suits, declarer can next play the 13th diamond and get both his hearts away for an additional, and valuable, overtrick.