2/1 game forcing (Two-over-one game forcing) is a bidding system in modern contract bridge in which, after a one-level opening bid, a non-jump response in a new suit at the two level commits the partnership to bidding at least game.
Normal 2/1 game forcing auctions
Exceptions to 2/1 game force
Some pairs don't play that 1♦-2♣ is game forcing, although some do. Also, 2/1 game forcing doesn't apply to a passed hand, or if there is an intervening bid or double by an opponent. Some pairs play that 2/1 isn't absolutely game forcing; the pair can stop below game only when responder rebids his suit. For example, 1♥-2♣; 2♥-3♣ is treated as nonforcing by some 2/1 players. A regular partnership should discuss this possibility.
1NT response forcing or semi-forcing for one round+
Because the two-level responses are stronger than in Standard American bidding, the response of 1NT to 1♥ or 1♠ opening 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 [[[Forcing notrump#Semi-forcing notrump|semi-forcing]]].
Other 2/1 features
Use of the 2/1 system usually implies (at least) the following additional agreements:
- Five card majors, i.e. major suit openings require at least a five-card suit;
- Limit raises of major suit openings, i.e. the jump raise 1♠ || 3♠ or 1♥ - 3♥ shows a game-invitational hand with at least four-card support (unless Bergen raises are used);
- Inverted minor raises, in which a jump raise of a minor suit opening is a weak preemptive bid, while a single raise is strong and forcing for one round;
- Jacoby transfers over 1NT opening;
- Jacoby 2NT, showing strong support with 4 or more cards;
- Splinter bids;
- New minor forcing;
- Fourth suit forcing and artificial.
Some also utilize Bergen raises.
|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.
|Forcing to game, with balanced hand and a good club suit.|
|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)
|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.
|Shows a very weak hand, perhaps 5-7 points, with at least four clubs.|
|Shows a weak hand, 5-9 points, with a long diamond suit.|
|Shows a weak hand, 5-9 points, with a long heart suit.|
|Shows a weak hand, 5-9 points, with a long club suit.|
|Shows 10-11 points without support for spades.|
|Shows 10-11 points with 3-card support for spades.|
||Shows 10-11 points with at least 4-card support for spades.|
|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.