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Even although most experts know them, we think it useful to give some explanatory examples of play tactics and the influence which the method of scoring has when applied to various tournaments.
Since duplicate bridge is different from a pairs tournament, it is evident that the tactics of play must be based on characteristics dissimilar and specific for each type of bridge.
In pairs tournaments your score is compared with the results of all the other pairs who had the same cards in each hand. And it is this comparison, and not the fact that the hand is positive or negative, which determines whether a score is good or poor.
The objectives therefore in duplicate play or in a pairs tournament (e.g. in BBO) when scores are assigned with IMPs are completely different from those of Mitchell pairs tournaments scored in MP’s. In a pairs tournament you must try to beat a good number of contestants (often the number is very high). In a team match you must try to beat only one opponent. In pairs tournaments one more trick can mean the difference between an average score and a top, or almost top. In duplicate on the other hand, an extra trick only gives 1 IMP. Thus small differences deriving from a contract being played as a trump contract or NT are significant in pairs tournaments, while they are negligible in duplicate.
Bridge in this kind of competition requires a tactic involving safety plays and the necessity to do everything possible to reach the contract, without giving importance to possible extra tricks. Pairs tournaments on the other hand require the opposite attitude, because both in play and in defense what counts is not maintaining the contract but the number of tricks made. This explains and justifies game plans which aim at obtaining overtricks but risk compromising the contract. For the same reason the defenders must ensure themselves as many tricks as possible, sometimes renouncing brave attempts to put the opponents down which if they don’t work, would permit the declarer to obtain overtricks.
In summary the main objectives in a duplicate or IMP tournament are:
– In play, do everything possible to maintain the contract
– In defense, do everything possible to defeat the contract
Obviously the method of play in duplicate bridge leaves more space for technical abilities, and therefore for technical improvement, and less space for luck than you need in pairs tournaments.
Bidding game when vulnerable or not vulnerable:
In IMP contracts the probabilities to consider which influence bidding a game which may be difficult to make, are strictly related to the fact of vulnerability. For example, bidding a difficult game when not vulnerable can give a result of 250 points (+420 instead of +170) which means 6 IMP. If you go down on a difficult game when not vulnerable you lose 190 points (-50 against +140), which 5 IMP. Therefore the favorable probabilities of bidding a difficult game when not vulnerable are only 6 to 5.
Bidding a difficult game when vulnerable has much better prospects when playing IMP. When you are vulnerable you can gain 10 IMP against a loss of only 6. It’s therefore evident that when vulnerable you must bid all game contracts which can reasonably be made, but when not vulnerable, only those which have legitimate prospects of being made.
Difference between SLAM when vulnerable or not vulnerable:
The position of vulnerability is no longer a determining factor since small slams, when vulnerable or not, are games which have just about equal favorable or unfavorable probabilities; you can win or lose practically the same number of IMP (when vulnerable 13, when not vulnerable 11).
Small swings and partial contracts:
Although it’s possible to lose a duplicate competition by 1, 2 or 3 IMP, normally you shouldn’t give undue importance to losing 1 or 2 IMP in a hand. If you have 90 pts playing a partial contract of 2 clubs or 2 diamonds, when you could have realized 120 points playing 2NT, it could be a poor score playing Mitchell but not influential in duplicate. The same can be said for gaining 100 points by putting down an opponents’ contract, instead of 110 or 140 playing your own partial contract.
Defense against game contracts:
Sacrifice contracts against opponents’ game contracts have better prospects playing Mitchell than in duplicate. In Mitchell you get an excellent result if you lose 300 points instead of 420, or else 500 instead of 620. In duplicate on the other hand, these sacrifices only give 3 IMP, not a good bet if there is a minimum chance of putting the opponents down. Bear in mind that if you make a false sacrifice with a loss of 500 points against an unrealizable opponents’ game when vulnerable, you lose 12 IMP. It’s obvious in any event that in any type of competition it’s advantageous to pay only 100 or 300 points against a game of the opponents when they are vulnerable.
Thus it’s convenient to go to a level of 5 when there are reasonable prospects of making 11 tricks, rather than accepting the prize of one down in the opponents’ sacrifice bid.
Sacrifice bids against Slam contracts:
Sacrifice bids against slam contracts can often save a sizeable number of IMP, particularly when you are in a favorable vulnerability position and when your pair has found a fit. Even going down by 5 tricks, equal to -1100 points, gives a gain of 8 IMP if your opponents can realize 1430 points.