This is a squeeze in three suits, one of which is
the trump suit. The strategy behind the knockout squeeze is that the declarer ruffs
the fourth suit in the long trump suit hand, thereby forcing the threatened defender
to choose between establishing the side suit of the declarer or allowing the declarer
to score an extra trump trick.
In the publication Adventures in Card Play, authored by Mr. Gezá Ottlik and Mr. Hugh Walter Kelsey, and published by Victor Gollancz, London, England, in 1979, both authors present the following argumentation, which is excerpted: The Knockout Squeeze is, in fact, the general form of the strategic squeeze against 'idle' trump cards, of which the Backwash Squeeze is a particular case.
Note: The cover of their publication is from a reprint by the Master Bridge Series published by Cassell in July 2005, ISBN-10: 0304368075 / ISBN-13: 978-0304368075.
And, as a conclusion, the distinguishing characteristic between the backwash squeeze and the knockout squeeze is emphasized as to whether the squeezed defender must play before or after third hand ruffs. By a knockout squeeze, the squeezed defender plays prior to the ruff, and by a backwash squeeze, the squeezed defender plays after the ruff.
Note: For the purists among the bridge players it also must be observed that the knockout squeeze does not threaten to promote and trumps held by the declarer to winners since they are often already of winning rank and are not threatened. Owing to this feature the knockout squeeze is also designated as a non-material squeeze. Other non-material squeezes include the entry squeeze, the one-suit squeezes, and the winkle squeeze.
The following illustration is presented by Mr. Geza Ottlik and Mr. Hugh Walter Kelsey in this publication:
South is the declarer. The auction is presented below: The contract is 4 Spades.
| West |
|
North |
|
East |
|
South |
| Pass |
|
Pass |
|
1  |
|
1  |
3  |
|
3 |
|
Pass |
|
4 |
| Pass |
|
Pass |
|
Pass |
|
|
The lead is the 2 of Spades, trump. The 8 of Spades in the dummy wins the trick. On the second trick, a small Heart is lead for the finesse, which succeeds. South then cashes the King of Clubs, plays to the Ace of Clubs in the dummy, and ruffs the remaining Club with the King of Spades.
With the play of the third Club, East is squeezed in three suits, even the trump suit.
On this position:
East's Option: If East decides to play a Spade, the trump suit, this play allows the South to win a trick with an eventual Diamond ruff in the dummy.
East's Option: A Heart discard allows South to establish a winning Heart in the dummy.
East's Option: A Diamond discard allows South to win a trick with his fourth Diamond.
If you wish to include this feature, or any other feature, of the game of bridge in your partnership agreement, then please make certain that the concept is understood by both partners. Be aware whether or not the feature is alertable or not and whether an announcement should or must be made. Check with the governing body and/or the bridge district and/or the bridge unit prior to the game to establish the guidelines applied. Please include the particular feature on your convention card in order that your opponents are also aware of this feature during the bidding process, since this information must be made known to them according to the Laws of Duplicate Contract Bridge. We do not always include the procedure regarding Alerts and/or Announcements, since these regulations are changed and revised during time by the governing body. It is our intention only to present the information as concisely and as accurately as possible.