Forcing Declarer to Ruff
By repeatedly leading a suit that declarer is void in, you force them to ruff. This shortens their trump holding, eventually leaving you with more trumps than declarer.
When defending a suit contract, the most powerful weapon you have is often your longest side suit. By repeatedly leading a suit that declarer is void in, you can force declarer to ruff, systematically destroying their trump control. This strategy is known as the "forcing defence".
Why it works
Declarer relies on having more trumps than the defenders to extract their trumps and safely cash side-suit winners. If you force declarer to ruff multiple times, their trump length dwindles. Eventually, a defender will be left with more trumps than declarer, taking control of the hand and cashing winning side-suit cards.
A worked example: Tapping the declarer
The Contract: 4♠ by South.
Your Hand (West):
♠ J 9 6 4
♥ K Q J 10 5
♦ A 5 2
♣ 3
11 HCP, four trumps.
Dummy (North):
♠ K 7 5
♥ A 4 2
♦ K Q J
♣ 8 6 5 4
13 HCP.
You lead the ♥K. Dummy wins the ♥A. At trick two, declarer plays the ♠K, and then a spade to their ace. You are now likely to score a trump trick with your ♠J-9, but you can do even more damage.
When you win the ♦A later in the hand, you must play another heart! Declarer is out of hearts and must ruff. Declarer started with five spades, but after ruffing, they only have two left. You also have two left! If you gain the lead again and play another heart, declarer ruffs again, leaving you with more trumps than declarer. The contract is ruined.
Four common mistakes
Switching to a new suit instead of continuing to "tap" (force) declarer.
Forcing dummy to ruff instead of declarer (ruffing in the short hand usually helps declarer).
Playing a forcing defence when your own trumps are very weak and partner has no trumps.
Panicking and trying to cash side-suit aces instead of continuing the forcing game.
When the rule does not apply
A forcing defence is usually ineffective if declarer has a massive trump fit (e.g., a 6-4 fit) because they have enough trumps to ruff safely without losing control. It is most effective when the defence holds four trumps in one hand against declarer's five.
Key takeaways
Lead your long suit to force declarer to ruff.
Reduces declarer's trump length.
Most effective when one defender holds four trumps.
Usually avoid forcing the short-trump hand; target declarer's long trumps.