Follow-up auctions -- meanings of opener's and responder's later rebids
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+ points, but it is not forcing to game.
The main advantage with this system is that it saves bidding room. 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.
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 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 possibilities. 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, you'll probably want to consult other resources. 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
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