This conventional defense method was devised by Dr. William Konigsberger and Mr. Derrick Deane, both of Geneva, Switzerland, approximately in the years 1938 and 1939. These two bridge personalities and game theorists were involved in the evolution of the game of bridge in Europe, especially in devising methods to communicate information by bids and calls to partner, upon which logical and reasonable deductions could be more easily made.
Side Note: Dr. William Konigsberger and his regular partner, Mr. W. Nye also of Switzerland, were already using the Gerber convention under a different designation when Mr. John Gerber was propagating this concept in the United States. Source is an article authored by the Bridge Columnist Mr. Alan Truscott of The New York Times newspaper, published July 23, 1988.
Note: Very little information has been uncoverd about the persons of Dr. William Konigsberger (Königsberger), Mr. Derrick Deane ,and also Mr. W. Nye. Any contribution of information as to these bridge players, especially photographs, would be greatly appreciated.
The devised defense method is constructed on the concept that a competitive overcall of 2 No Trump shows and promises any pair of unbid suits by a player whose side has not yet bid.
Important Note: The reader should read the above parameter of this concept again, and note that the employment of the Geneva conventional defense method is possible by a defending player, whose side has not yet bid, meaning that one player of the partnership may have made a call, such as pass or, very rarely, a double.
The overcall of 2 No Trump promises a two-suited holding, and the competitive action is based more on the strength of the distribution than on high card points. An illustration should clarify this defense method.
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1  |
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2 NT |
| East |
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South |
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Meaning |
| 1 |
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Promises opening values. |
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2 NT |
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Geneva Convention. With an immediate overcall of 2 No Trump South shows a two-suited holding, and conveys the information that the shape of the holding is 5-5-2-1. The overcall also promises distributional strength. (Note: although unknown it is doubtful whether or not Dr. William Konigsberger and Mr. Derrick Deane permitted such an overcall when holding a void.) |
Although the original version of their concept is not, or no longer available since there was no official publication, it is logical to assume that the length of the two suits should preferably be a 5-5 shape by equal or unfavorable vulnerability. This shape may have well been reduced to a 5-4 shape in the case of favorable vulnerability, which would allow the partnership to compete more often.
Note: Any other opening bid on the one level followed by a 2 No Trump overcall would also show a two-suited holding.
Note: In The Official Encyclopedia of Bridge, as published by the American Contract Bridge League, the fact is mentioned that the overcall could theoretically be employed on the three level. Such a defense action would occur in the fourth seat following two suits bid by the opposing side, with partner passing after the initial opening bid. For example:
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South |
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West |
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North |
1  |
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Pass |
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2 |
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3 NT |
The overcall must be a jump to a higher level in order to fall within the established guidelines of the Geneva conventional defense method. Without the jump overcall the bid of only 2 No Trump, in this particular bidding sequence, would promise a No Trump holding with balanced distribution, stopper(s) in Hearts, and the agreed range for a No Trump overcall.
As the reader can easily surmise, conclude, and deduce the defense method may force the partnership to a higher than desired level, whereby the danger of being doubled by the opposing side would only increase.
Continuances
The advancer, upon realizing that partner has a two-suited holding, will bid accordingly if both suits can be inferred. There is no mention as to whether any such continuance by the advancer would be forcing or even invitational. A possible agreement, with an exceedingly excellent fit in both suits, would be that a jump bid would be game forcing, especially if a Major suit fit can be found.
Otherwise, if both suits are not known, then the advancer bids his best suit among the three unbid suits. Since the overcaller is showing at least two of these three unbid suits, then the percentage of finding a fit is indeed high. However, if the suit bid by the advancer is not one of the two suits held by the overcaller, then the overcaller will bid the cheaper of the two held suits. In this case the advancer can either pass with good support or correct to the now known second suit of the overcaller.
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.