Follow-up auctions -- meanings of opener's and responder's later rebids
Forcing Notrump convention (new page)
One of the most popular bidding systems in the U.S. is the 2-over-1 Forcing-to-Game system. It's based on Standard American with 5-card majors. The main difference is in the meanings of 2-level responses to a major-suit opening.
The general approach is just as the name suggests: If responder's first bid is 2 of a new suit (1S by opener - 2C, 2D or 2H by responder), it sets up a forcing auction; the partnership must bid on to game level. This is different from old-fashioned Standard American, where a 2-level response promises a good 10 or more points, but is not forcing to game.
The main advantage of the 2-over-1 system is that it saves bidding space. After making the initial 2-level response, responder doesn't have to jump to show forcing-to-game values. Because the auction can stay low, opener and responder have more room to exchange information below game level and more ways to evaluate slam possibilities.
One of the disadvantages is that there's no easy way to show many invitational hands of 10-11 pts. To describe these hands, you must use the Forcing Notrump convention, which is a key part of the 2-over-1 system.
The 2-over-1 system is more complex than it may seem. Even though the basic principle sounds fairly straightforward, the auctions can become quite complicated, especially when you're investigating slam contracts. Forcing Notrump auctions can also be difficult unless you have a clear understanding of all the possible follow-ups.
The summary below is intended as a basic introduction to 2-over-1 agreements. There's much more to the system than can be covered here, so if you're serious about learning its finer points and popular variations, you'll want to consult other sources. Here are some recommended books and software packages that offer more detailed analysis:
25 Steps to Learning 2-over-1 by Paul Thurston
Workbook on the Two-Over-One System by Mike Lawrence
Two-over-One Game Force by Max Hardy
Standard Bridge Bidding for the 21st Century by Max Hardy
Understanding 1NT Forcing by Marty Bergen
2 Over 1 Game Force by Eric Rodwell and Audrey Grant
Interactive CD software: Two-Over-One System by Mike Lawrence
2-over-1 forcing-to-game is "on" only when your side opens 1H or 1S in 1st or 2nd seat and the next player passes and responder makes a non-jump bid of 2 of a new suit. The only relevant auctions are:
1-2 1-2 1-2 1-2 1-2
You may also choose to play the auction 1-2 as forcing to game, but you'll want to make other modifications to your system. The Forcing Notrump response is not used after a 1D opener, so if you specify that a 2C response is a game-force, you need to define how you'll show an invitational hand with clubs. You can describe some of these hands by adding the agreement that the auction 1D-3C -- or the auction 1D-2C-2D-3C -- is invitational (10-11 pts., 6+-card suit). If partner opens 1D and you hold invitational strength with only five clubs, a jump to 2NT will usually be the best alternative for your first response.