Bridge is all about reading the distribution of the hand both as declarer and defender. Of course as declarer, you need to judge which defender is more likely to have which suit but as a defender, all you have to judge is the declarer's distribution both from his bidding and your partner's signals while the play is on.
Sometimes its not easy to read with absolute certainty what the declarer holds but mostly there is a clue available on reasonable assumption made out of declarer's bidding and of course your partner's intelligent co-operation.
Today's defence rests on such an assumption that is as reasonable as accurate. South bid as follows:
The following dummy came to your right, sitting as east:
The opening lead was of course the JC taken by your KC. Well as west how do you visualise the defence. You know you have one club trick, possibly two if declarer has doubleton clubs, which can be a bit dicey looking to his bidding where he has promised a 6-5 majors hands, or 5-5 majors hands.
How about assessing declarer's high card points. Well he certainty has QC, and his remaining 11 or 12 points need to be in the majors. If there are no trump losers giving declarer the AK of hearts, leaves declarer's spades pretty wide open, headed either by K or A since declarer has shown a minimum hand looking to his bid of 3H. With 2 top spade honours out of 3 he would surely have bid 4H instead of 3H holding 15+. Of course if a trump top honour is missing from the declarer's armoury it would have to be a singleton K or A in partner's hand, which of course could spell doom for the declarer if the singleton K of hearts presumed with partner held on finesse.
Of course if partner holds the ace of hearts, the contract is doomed in any case if declarer has a doubleton club for partner surely will take one spade trick, come what may. So with one spade trick 2 clubs and a possible singleton trump honour scoring, declarer has little chance to succeed. On the contrary if there are no trump losers, giving declarer the top trump honours, then most likely partner is sure to score 2 spade tricks, which could again spell curtains for the declarer, provided you get your timing right before the declarer gets an opportunity to discard his losers on the awesome battery of solid diamonds staring at you from the dummy.
Well what do you make of it? On the KC declarer droops the QC. Does this ring a bell for the defence? West has a very tempting return option after taking the KC, in shifting to a spade. The declarer could well hold KJXXX under your partners AQX, which can straight away set the contract down with 2 spade tricks and the third spade ruffed.
At the original table east misdefended on a hasty judgement even after cashing the AC, which to his luck held. Surely now the defence was reasonably safe and shining. Can you make the right choice now? Well this west shifted to the 5 of spades as all normal mortals would do to the lowest of dummy and the declarer picked the ace of spades, knocked out the trumps and claimed 4 more diamond tricks, which added to his 5 trumps and ace of spades gave him the contract.
The defence slipped although after sougth follows to the 2 clubs, west must go for the scissor coup by severing the diamond link on play of 10D, on the simple logic that declarer would then not be able to draw out west's 4 trumps and end in dummy to run the diamonds. With the diamond linkage severed, he can't afford to get his fragile spades discarded. If you were afraid that declarer could have been void in diamonds, you were in a delusion for then he would hold 6 spades, which would give him a solitary spade loser with his contract safe. West's downfall was not due to a mere lack of courage but to the lack of the courage of conviction.
===============================
South West North East
1S P 2D P
===============================
2H P 3C DBL
3H P 4H ALL PASS
===============================
====================
North East
====================
Dummy 54
863 7643
QJ2 102
AKQJ4 AK852
76
====================