2/1 game forcing (Two-over-one game forcing) is a bidding system in modern contract bridge structured around the following responses to a one-level opening bid: The 2/1 game force does not apply to responses by a passed hand, or if there is an intervening by an opponent. Other responses are per Standard American methods in accordance with.

Game forcing auctions

The 2/1 auctions are: 1–2, 1–2, 1–2, 1–2, 1–2, and 1–2.

Variations

The following variations may be made by :

1NT response to major suit opening

Because the two-level responses are stronger than in Standard American bidding, the response of 1NT is forcing for one round and is used (among other things) for weaker hands containing low-ranking suits. Since the 1NT response is forcing, hands with a three-card limit raise can start with 1NT and later jump-support partner. See Forcing notrump for additional details. Some pairs play a variant in which the 1NT response to 1 or 1 is semi-forcing. Since opener has been forced to rebid on hands which he might otherwise have passed, he may have to rebid in a new suit with only three or even two cards.

Other features

Use of the 2/1 system usually implies (at least) the following additional agreements:

Examples

1 – 2 2 – 2 Forcing to game, with original spade support and good club suit. This is different from standard bidding, in which such a sequence would show about 10 points, and club suit could be semi-fake. 1 – 2 2 – 2NT. Forcing to game, with balanced hand and a good club suit. 1 – 2 2 – 3 Forcing, unless the partnership has agreed that this is an exception to the "2/1 rule." 1 – 2 Forcing for one round only (as in Standard American), except in the variant of 2/1 where this sequence is game forcing as well. 1 – 2 Forcing for one round; 10 points or more with at least four clubs. 1 – 3 Weak; 9 points or less—sometimes much less—with at least five clubs. 1 – 2 Weak; 6-9 points with at least 3 hearts (unless Bergen raises are in use, in which case it shows precisely 3 hearts) 1 – 1NT; 2 – 2 Shows a weak hand, 6-9 points, with precisely two spades. Some also use this for an extremely weak hand (0-5) with three spades. 1 – 1NT; 2 – Pass Shows a very weak hand, perhaps 5-7 points, with at least four clubs. 1 – 1NT; 2 – 2 Shows a weak hand, 5-9 points, with a long diamond suit. 1 – 1NT; 2 – 2 Shows a weak hand, 5-9 points, with a long heart suit. 1 – 1NT; 2 – 3 Shows a weak hand, 5-9 points, with a long club suit. 1 – 1NT; 2 – 2NT; Shows 10-11 points without support for spades. 1 – 1NT; 2 – 3 Shows 10-11 points with 3-card support for spades. 1 – 3 Shows 10-11 points with at least 4-card support for spades. 1 – 1NT; 2 – 3 Shows 10-11 points with a long heart suit. 1 – 2 This is a jump response, and there are different ways of handling it. In Standard American, such a "jump shift" shows a very strong hand and is unequivocally forcing. However, since such hands do not occur with great frequency, it is more common today to use such a bid to show a weak hand with a long suit, unsuitable for defense. Another possibility is to play it as a "fit-showing jump", showing 8-10 points, a decent heart suit, and good diamond support.