The trump coup can be explained in many ways, but the conclusion is the same. The trump coup is a special or unusual play maneuver or play tactic. The trump coup generally refers to an endplay situation or lay of the cards between a declarer and one defender, whereby the finesseable trump cards of a defender are trapped without a finesse.
Choice of Presentation
In practically all circumstances the trump coup is initiated and accomplished by the declarer, and it is from this perspective that the information on this page is presented. The accomplishment of the trump coup is achieved by the declarer winning tricks in a side suit. The idea is that if the next player in rotation from the declarer ruffs with a trump card, then the declarer, void in dummy, overruffs. Otherwise the declarer plays in a manner as to sluff losing tricks in the side suits.
The most important feature to remember is the fact that if the declarer sluffs losing tricks in a side suit before reducing trumps and the next player in rotation refuses to ruff, then the declarer would have to ruff a card in the dummy. In this situation the declarer would become endplayed, since the declarer would have to lead a trump to one of the higher trump cards held by the next player in rotation.
This particular play technique can be found in publications about the game of Whist, which is a predecessor of the game of bridge. Below is the publication by Mr. Henry Jones, aka Cavendish, called Cavendish on Whist, printed in 1880, page 254. The rudimentary elements of the trump coup is illustrated. The visitor must make allowances for the poor quality of this depiction since it has been taken from the new and revised 12th edition of the publication.
The publication of Mr. Louis Watson, titled Watson's Classic Book on the Play of the Hand at Bridge, the New Edition, enlarged and modernized by Mr. Sam Fry, Jr., published in the year 1958, describes clearly and succinctly the trump coup in the following quoted words:
The trump coup is not confined to situations, in which only one honor is missing. Even what seems like a rather innocuous combination of cards, such as that in the following diagram, may present a coup situation:
The lead is in the dummy, North - let us assume that to have the lead there at this point was pre-arranged by the declarer; dummy, of course, holding no trumps. The hand has actually been couped, for in this situation South must make a trick with his Ten (the Ace and Jack already having been played). If the lead is in the South hand at this point, no tricks at all can be obtained in this suit (trumps).
The trump coup is applicable to any combination of cards resembling a tenace, whenever a finesse is impossible. It depends, of course, on learning that the right hand opponent holds the missing honors under your own tenace, and on being able to lead from the dummy at a time when he must play before you - or ruff before you, to be more exact. Two things must always be remembered, namely, that the opponents must be prevented from discarding if possible, and that the number of entries to the dummy must be one more than the number of times it is necessary for the declarer to shorten himself in trumps.
Trump Coup upon Discovery of Trump Split
The contract is 6 Spades and the declarer is South. Counting the variables once the dummy is tabled South realizes that he must prepare for a bad trump split. If West holds the trump cards J763 or even J7643, then the contract is doomed from the beginning. However, if East holds either of these two combinations, then South can only fulfill the contract with the execution of a trump coup.
It is upon the basis of this assumption that South begins declaring the contract following the lead of 
10. East wins with the Ace and returns a Diamond, which South wins. South then, on the third trick, plays the 
Ace and King and discovers that West held only one trump card. South is now certain that only a trump coup can successfully ensure the contract.
South ruffs then a Heart in order to reduce his trump length to the trump length of East. South then takes the 
King, leads the 2 to the Jack, and continues with the 
King.
If East were in a position to ruff, then South would overruff, draw the remaining trumps, and claim. But, if East follows, as in this example, South is able to discard the Ace and lead the Queen.
East is in a peculiar position to ruff, but realizes that nothing can be gained by ruffing, and thus discards. South therefore discards the last remaining Diamond.
At trick 12, with the dummy to lead, South holds Q10 behind East's holding of trump J7. Whatever East does, East cannot win a trump trick. The trump coup is the only successful play in order to fulfill the contract.
Note: South will fail to fulfill the contract unless South begins to shorten the number of his trump cards by trumping a Heart early in the play, and then reducing again the number of trump cards to equal the number of trump cards held by East.
At the 86th Fall North American Bridge Championships conducted in the city or Phoenix, Arizona, between November 28 and December 6, Mr. Li-Chung Chen executed a trump coup on the following deal. The article is provided verbatim for the convenience of the visitor.
Bringing It Home: On this deal from the first semi-final session of the Kaplan Blue Ribbon Pairs, Li-Chung Chen of Cupertino, California, United States, took advantage of a subtle error by the defense to land a difficult contract in spectacular fashion. Mr. Li-Chung Chen, East, was playing with Mr. Ari Greenberg of Menlo Park, California, United States.
| West |
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North |
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East |
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South |
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Pass |
| 1 |
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Pass |
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1 |
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1 |
| Dbl (1) |
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Pass |
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4 |
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Pass |
| Pass |
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Dbl |
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All Pass |
(1) Three-card Heart support.
South started with the 10, ducked to North's King. At this point, North must switch to a Club to defeat the contract, but that is far from clear - and his partner did not overcall Spades, making a switch to that suit at trick two perfectly normal.
Mr. Li-Chung Chen went up with the Ace and played a low Heart from hand, South pitching a Spade. North took dummy's Queen with his King and continued with a Spade to South's King.
When South exited with a Diamond, Mr. Li-Chung Chen won the Queen and played dummy's 6 to the 7, i and a low Diamond from South.
Mr. Li-Chung Chen played a Club to dummy's Jack, followed by dummy's last Heart, covered by the 9 and 10, South discarding his last diamond. Mr. Li-Chung Chen then played his third Diamond to the Ace in dummy. This was the end position:
When Mr. Li-Chung Chen played the Jack, North had no answer. If he discarded a Club, Mr. Li-Chung Chen would also pitch a Club, cash the Ace and catch North in a trump coup at trick 12. In practice, North ruffed with the 2, and when Mr. Li-Chung Chen overruffed, South was squeezed in the black suits.
Plus 790 was good for 75 our of 77 matchpoints for Mr. Li-Chung Chen and Mr. Ari Greenberg, who qualified for the Blue Ribbon final and finished 20th overall.
Switching to a Club allows the defenders to play the suit twice, breaking up the squeeze that caught South in the end.
Brian Gunnell - Bridge Bites
Mr. Brian Gunnell authored an article about the trump coup, which can be found on the website for ACBL. The presented contract is 6 Spades and Mr. Brian Gunnell describes how, with a little bit of magic, a certain trump loser evaporates into thin air thanks to some will-timed declarer play. Archived.
Richard Sampson - Twojacks
Of London, England, Mr. Richard Sampson is an online bridge instructor and a champion of multiple tournaments such as the Lederer, the Crockford, and the Spring Fours. His article about the trump coup deals with a bid grand slam of 6 Hearts. Archived.
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.