Mr. John Mohan is the only player to win two World Championship titles in the year 2000. He has earned 17 North American titles and also has three wins in South America and four in South Africa to his credit. He was also selected as the ACBL Player of the Year 1999. This defensive method carries his surname and was devised by him.
Note: There are variations of the Mohan Defense convention and they are somewhat dependent on the bidding system employed and can be altered or varied to meet the requirements of the particular bidding system.
Note: Some partnerships have agreed that the distribution of the holding, when overcalling could / may be reduced to 4-4 in both Major suits regardless of the state of vulnerability, otherwise the distribution is generally 5-4, 4-5, or 5-5 depending on the state of vulnerability. This is entirely a partnership agreement in all employed variations of the concept.
The original concept behind this defense method is the fact that it is employed by partnership agreement against Weak No Trump openings by the opponents. In defining a Weak No Trump, a strong No Trump opening is considered to contain 16 high card points and, in this instance, also 13-15 high card point No Trump openings by partnerships, which use Big Club systems as part of their partnership agreements.
All other No Trump openings are considered weak. The fundamental thought behind the Mohan defense method is to use transfers so that the overcaller has a second opportunity to bid, especially with a moderate to good holding.
The following chart shows the overcall and the meaning of the overcall:
Opener Overcaller Meaning 1 NT Weak No Trump; generally 12-15 points. Double Promises a good 14+ points, generally a balanced holding. Generally converted to penalty. 2 Promises both Major suits. 2 A transfer to Hearts. 2 A transfer to Spades. 2 Promises Spades and an unspecified Minor suit. 2 NT Promises Hearts and an unspecified Minor suit. 3 This overcall is natural and means long Clubs, generally 5/6-card suit. 3 This overcall is natural and means long Diamonds, generally 5/6-card suit. 3 This overcall is natural and means long Hearts, generally 5/6-card suit; also preemptive. 3 This overcall is natural and means long Spades, generally 5/6-card suit; also preemptive.
In order to make such an overcall, according to the above scheme, the overcaller should have at least a sound opening, or a holding which would have demanded an opening had the opponent not first entered the auction with a Weak No Trump opening. An advantage of the transfer bids is that, if the partner of the overcaller becomes the declarer, then the Weak No Trump bidder must lead up to the declarer. The preemptive bids should have the appropriate length according to the state of the vulnerability and the number of losing tricks. The distributional points are also calculated and evaluated.
The action of the advancer, the partner of the overcaller, can be considered diverse in substance and is generally a matter of partnership agreement. The decision, whether to play system on or system off, is left to the individual partnership. Included below are some suggestions for a partnership understanding, but this is only a suggestion.
If the partner of the Weak No Trump bidder redoubles for business, then a Pass is to play. The partnership agreement is that system is off.
Following a double, the next double is Takeout, usually showing exactly two cards in their suit. Other partnerships prefer that the first double is only semi-natural and simply shows extra values.
Once the Weak 1 No Trump opening is doubled, then the understanding should be that all bids are demanding up to and including 2. Other partnership agreements prefer up to and including 2. The difference in these understandings is the fact that the force through to 2 may cause the partnership to reach an unmakeable contract on the three level.
If the overcall is 2, and the first response by the advancer is 2, this first response shows no or little preference. This can become advantageous if the overcaller holds a distribution of 5-4 in both Major suits. It is generally a normal understanding that a first response by the advancer of: (a) 2 No Trump is a natural game try; (b) Jumps are invitational; (c) 3 is to play; and (d) 2 followed by 3 is forcing.
It is recommended that, if the partner of the Weak No Trump bidder passes a transfer bid by the overcaller, then the advancer must accept the transfer. Any first bid of a new suit becomes a natrual bid and are considered to be one-round forcing. A first response of 2 No Trump is a natural game try and Jump Acceptances after transfer overcalls are invitational, not forcing.
In response to 2 showing Spades and an unknown Minor suit, 2 No Trump is an artificial game try, asking for size and to identify the Minor suit. 3 is pass or correct and 3 is invitational.
After an overcall of 2 No Trump, promising Hearts and an unknown Minor suit:
3 : is either pass or correct 3 : is natural and forward-going 3 : is to play 3 : is natural and forcing
These suggestions are just that: suggestions. The individual partnership may reach a different understanding and/or agreement more suitable to their existing agreement. However, there is one feature of the Mohan Defense mechanism, which stands out. If the overcaller makes a transfer overcall of 2 or 2, and then rebids a Minor suit, even if it is Diamonds, then the overcaller promises a 4-card Major suit and a 6-card Minor suit.
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.