2/1 Game Forcing

2/1 game forcing (Two-over-one game forcing) is a bidding system in modern contract bridge, where a non-jump two-level response to a one-level opening bid commits a partnership to at least the game level. It is based on Standard American bidding and has largely superseded it; the principal difference is that a full opening bid is required for a response at the two level to an opening bid of one of a major. Thus, the response of 1NT to 1♥ or 1♠ opening is forcing or semi-forcing.

Some pairs don't play that 1♦?2♣ is game forcing (although some texts recommend that approach). 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 nonforcing by some 2/1 players. A regular partnership should discuss this possibility.

The 2/1 auctions are 1♥?2♣, 1♥?2♦, 1♠?2♣, 1♠?2♦, and 1♠?2♥. Hands without an opening bid are required to respond 1NT to 1♥ or 1♠. In Standard American, 1NT response is nonforcing, but in 2/1 it is forcing for one round of bidding. Since this bid is forcing, hands with a three-card limit raise can start with 1N and later jump-support partner. See Forcing notrump for additional details. One variant employed is to play 1NT response to 1♥ or 1♠ as semi-forcing.

Most pairs combine these basic features of 2/1 system with one or more of the following conventions:

• Jacoby transfers over 1NT opening,
• Jacoby 2NT, showing strong support with 4 or more cards
• Splinter bids

Example sequences

1♠ ? 2♣
2♦ ? 2♠
Forcing to game, with original spade support and good club suit. This is different than in 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♣
1♦ ? 3♣
Forcing, unless the partnership has agreed that this is an exception to the "2/1 rule."

1♦ ? 2♣
Forcing for a round only (as in Standard American), except in the variant of 2/1 where that sequence is a game forcing as well.

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♦ ? 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 spade suit, and good diamond support.