This conventional defense method was developed by Mr. Mats Nilsland and Mr. Rolf-Eric Andersson in the year 1974. The basic concept is two-fold in that an opening bid in a Major suit shows exactly 4 cards and attempts to conceal a balanced to semi-balanced holding from the opponents. The concept for the former purpose of showing distribution became abandoned and emphasis was placed on the method as a defense method against the opening of No Trump by an opponent.

Basic Concept

The basic concept or structure of A:son 74, an abbreviation for Andersson, one of the developers and the last two digits of the year, was developed for interference following a 1 No Trump opening by an opponent. In essence the defense method employs a similar structure to the responses of Stayman, Transfer Bids, and also Minor Suit Stayman.

Norwegian Description: Konstruerat av Rolf-Eric Andersson och Mats Nilsland av 1974, därav systemets namn. Högfärgsöppning visar precis fyra kort i färgen och utgör grunden i systemet. Därmed lämpar sig A:son kanske speciellt väl för partävling. Source.

Also: Systemet är en kombination av naturlig och artificiell budgivning. Vissa principer är genomgáende och gäller i flertalet situationer. (Translation: The system is a combination of natural and artificial bidding. Some principles are more comprehensive and applies in most situations.)

Note: The photograph of Mr. Mats Nilsland below is from the year 2004. Any contribution of a photograph of Mr. Rolf-Eric Andersson would be greatly appreciated.

     

Defense Method

Following an opening of 1 No Trump by an opponent the partnership can enter the auction with the correct distribution and strength. As stated, this competition occurs with the employment of Stayman, Minor Suit Stayman, and also Transfer Bids, which are shown below, and which is the basic outline for competing.

Note: This defense method is normally employed if the range of the No Trump opening is considered weak, normally a range between 10 and 15 points. If the range announced exceeds this range, then the partnership must make certain adjustments to the invitational and one-round forcing bids. In addition the power of distributional patterns must be increased in ratio to such No Trump ranges.

Opponent   Intervenor   Meaning
1 NT   Double   The double is penalty-oriented.
    2 Clubs   This bid is artificial and is similar to a Stayman bid. It promises either a two-suited holding in both Major suits or a minimum of 3-3 distribution in both Major suits and a long, unspecified Minor suit.
    2 Diamonds   This is a transfer overcall to Hearts and promises a minimum of a 4-card Heart suit.
    2 Hearts   This is a transfer overcall to Spades and promises a minimum of a 4-card Spade suit.
    2 Spades   This bid is artificial and is either a Stayman-style overcall for both Minor suits or one unspecified Minor suit.

Continuances

Following the competitive overcall the advancer follows certain guidelines. These guidelines are in effect if the partner of the No Trump bidder indeed passes. However, if the partner of the No Trump bidder also competes following the immediate overcall, then the partnership should have an agreement as to whether to play systems on or systems off depending on whether the competitive action of the partner of the No Trump bidder has interfered with the effectiveness of the agreement.

For all intents and purposes of this presentation the partner of the No Trump bidder passes following an immediate double and/or suit overcall. This allows the advancer to effectively compete according to the following guidelines of A:SON 74 defense method.

As developed and devised by Mr. Mats Nilsland and Mr. Rolf-Eric Andersson the responses and rebids by the intervenor are shown below for all possible overcalls:

Opponent   Intervenor   Responder   Advancer   Meaning
1 NT   2 Clubs   Pass       This bid is artificial and is similar to a Stayman bid. It promises either a two-suited holding in both Major suits or a minimum of 3-3 distribution in both Major suits and a long, unspecified Minor suit.
            2 Diamonds   The bid of the next higher Minor suit denies possession of any 4-card Major suit. The intervenor rebids:
Pass: A pass shows a one-suited holding with Diamonds. The suit must contain at least 5 cards.
2 Hearts: This shows a two-suited holding with both Major suits. By bidding Hearts first the intervenor promises a better suit in Hearts and/or both Major suits of equal quality. This shows a two-suited holding with both Major suits. By bidding Hearts first the intervenor promises a better suit in Hearts (Partnership agreement may convert to a 5-4 distribution.)
2 Spades: This shows a two-suited holding with both Major suits. By bidding Spades first the intervenor promises a better suit in Spades. This shows a two-suited holding with both Major suits. By bidding Hearts first the intervenor promises a better suit in Hearts
2 NT: This rebid guarantees a distribution of at least 5-5 in both Major suits plus sufficient values to sustain a contract on the three level against a No Trump opening by opponents.
3 Clubs: This bid is natural and preemptive. The intervenor promises a long suit (semi-broken) in Clubs.
3 Diamonds: This bid is natural and preemptive. The intervenor promises a long suit (semi-broken) in Diamonds.
            2 Hearts   Promises a 4-card Heart suit or a distribution of 1-3 in both Major suits. The rebids of the intervenor are:
3 Clubs: Promises a 6-card Club suit with only 3-card support in Hearts, the suit bid by advancer.
3 Diamonds: Promises a 6-card Diamond suit with only 3-card support in Hearts, the suit bid by advancer.
            2 Spades   Promises a 4-card Spade suit. The rebids of the intervenor are:
3 Clubs: Promises a 6-card Club suit with only 3-card support in Spades, the suit bid by advancer.
3 Diamonds: Promises a 6-card Diamond suit with only 3-card support in Spades, the suit bid by advancer.
            2 NT   This first response by the advancer promises at least one 4-card Major suit and values to bid on the three level. This response is forcing for one round, but it is not game forcing. The intervenor has then the opportunity to more clearly define the distribution:
3 Clubs: Natural. Denies a 5-card Major suit. Diamonds is the better Minor suit.
3 Diamonds: Natural. Denies a 5-card Major suit. Clubs is the better Minor suit.
3 Hearts: Shows minimum values and possession of both Majors with at least a 4-4 distribution.
3 Spades: Shows maximum values and possession of a 5-card (plus) Spade suit and a 4-card (plus) Heart suit.
4 Clubs: This is an exclusion rebid showing a void in Clubs and length (minimum of 5-5) in both Major suits. Opposite a No Trump opening by an opponent this is also a mild slam try.
4 Diamonds: This is an exclusion rebid showing a void in Diamonds and length (minimum of 5-5) in both Major suits. Opposite a No Trump opening by an opponent this is also a mild slam try.
4 Hearts: Shows maximum values and the possession of 5-card Heart suit and a 4-card Spade suit.
            3 Clubs   This first jump response by the advancer is natural, promises long Clubs, and also one-round forcing. The response is not preemptive, but rather value-showing.
            3 Diamonds   This first response by the advancer is natural, promises long Diamonds, and also one-round forcing. The response is not preemptive, but rather value-showing.
            3 Hearts   This first jump response in Hearts promises at least a 5-card Heart suit and is only invitational, not forcing.
            3 Spades   This first jump response in Spades promises at least a 5-card Spade suit and is only invitational, not forcing.

Continuances for an overcall of 2 Diamonds or 2 Hearts are shown in the following schematic:

Opponent   Intervenor   Responder   Advancer   Meaning
1 NT   2 Diamonds   Pass       This is a transfer overcall to Hearts and promises a minimum of a 4-card Heart suit.
    2 Hearts   Pass       This is a transfer overcall to Spades and promises a minimum of a 4-card Spade suit.
            2 Hearts   The advancer accepts the 2 Diamonds transfer bid.
            2 Spades   The advancer accepts the 2 Hearts transfer bid.
                 
1 NT   2 Diamonds   Pass   2 Hearts   Following the acceptance of the transfer bid to Hearts the intervenor can continue to exchange information about the holding:
Pass   Pass           A pass by the intervenor shows minimum values and a willingness to play in either 2 Hearts or 2 Spades.
    2 Spades           Following a transfer bid to Hearts the intervenor can rebid 2 Spades to show a holding with 5 Hearts and 4 Spades and sufficient values to allow advancer to decide the best contract.
    3 Clubs           Following a transfer bid to Hearts the intervenor can rebid 3 Clubs to show a holding with 5 Hearts and 4 Clubs and sufficient values to allow advancer to decide the best contract.
    3 Diamonds           Following a transfer bid to Hearts the intervenor can rebid 3 Clubs to show a holding with 5 Hearts and 4 Clubs and sufficient values to allow advancer to decide the best contract.
    2 NT           A rebid of 2 No Trump promises the 4-card Heart suit and a longer side suit, which can also be Spades, but generally a lower-ranking side suit.
                 
Opponent   Intervenor   Responder   Advancer   Meaning
1 NT   2 Hearts   Pass   2 Spades   Following the acceptance of the transfer bid to Spades the intervenor can continue to exchange information about the holding:
    3 Clubs           Following a transfer bid to Spades the intervenor can rebid 3 Clubs to show a holding with 5 Spades and 4 Clubs and sufficient values to allow advancer to decide the best contract.
    3 Diamonds           Following a transfer bid to Spades the intervenor can rebid 3 Diamonds to show a holding with 5 Spades and 4 Clubs and sufficient values to allow advancer to decide the best contract.
    3 Hearts           Following a transfer bid to Spades the intervenor can rebid 3 hearts to show a holding with 5 Spades and 4 Hearts and sufficient values to allow advancer to decide the best contract.
    2 NT           A rebid of 2 No Trump promises the 4-card Spade suit and a longer side suit.

Continuances for an overcall of 2 Spades are shown in the following schematic:

Opponent   Intervenor   Responder   Advancer   Meaning
1 NT   2 Spades   Pass       This bid is artificial and is either a Stayman-style overcall for both Minor suits or one unspecified Minor suit.
            2 NT   Promises either equal length in both Minor suits or a longer Diamond suit.
Pass   3 Clubs           The intervenor shows a longer Club suit; both Minor suits may be of equal length, but the quality of the Club suit is better.
    3 Diamonds           This rebid promises invitational values, generally for a No Trump contract, and a Club suit of good quality.
    3 Hearts           A rebid in Hearts is natural and one-round forcing.
    3 Spades           A rebid in Spades is natural and one-round forcing.

 

 

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.

 


     
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