Morton's fork coup

Morton's Fork is a coup in contract bridge that forces an opponent to choose between:

It takes its name from the expression Morton's Fork.

It appears that South has both a heart and a club loser. Although South can establish another winner in diamonds, just one discard on a diamond honor doesn't help.

N

W               E

S

South receives the lead of the ♦J against 6♠. However, there are two ways that the contract can be made. South might manage to avoid any heart loser. Or, South might take two heart tricks; in that case, South could discard one club on the ♥K and another club on a diamond honor.

Judging from the opening lead that East holds the ♦A, South plays the ♦9 from dummy at the first trick, ruffs in hand, and draws trumps. Hoping that West holds the ♥A, South leads the ♥7, executing Morton's Fork:

Note that declarer must be careful not to play a high diamond on the opening lead, as East could then withhold the ace. That would force the declarer to choose a discard prematurely. South must get a discard on a diamond honor eventually, but not before West has been forced to decide whether to take the ♥A or duck it. Only then will South know whether to discard a heart or a club on the diamond winner.

N

W               E

S

Robert Gray gives this spectacular example of an impossible defense to Morton's Fork. West leads the ♣2 against South's six club contract. South wins and initiates the coup by leading the ♠8.

If West takes the ♠A, he might as well continue with the ♣3. South wins and leads a heart, covered and ruffed. A third club to South's hand, and another heart, again covered and ruffed. A diamond to South's hand, and a third heart covered and ruffed. The ♠K is cashed, and then another diamond to South's hand allows dummy's last two losing diamonds to be discarded on the ♠Q and the established heart.

...
Wikipedia