Grand slam force Grand slam force The Grand Slam Force is a bidding convention in contract bridge that was developed by Ely Culbertson in 1936. It is intended to be used in cases where the combined hands of a partnership are so strong that a slam (winning at least 12 tricks) is a near-certainty and a grand slam (winning all 13 tricks) is a possibility. It allows one partner to gain information on the quality of trumps in the other partner's hand. When this convention is in force, a bid of 5NT (five notrump), when it does not conflict with other conventions used
History of contract bridge clubs or spades); and there were slam bonuses. Despite the popularity of whist, this game, and variants of it, "bridge" and "bridge-whist", became popular in the United States and the UK in the 1890s. In 1904 auction bridge, known for a time as "royal auction bridge", was developed where the players bid in a competitive auction to decide the contract and declarer. The object became to make at least as many tricks as were contracted for and penalties were introduced for failing to do so. The modern game of contract bridge was the result of innovations to the scoring of