Inverted minors refers to a treatment introduced by the
Kaplan–Sheinwold
The Kaplan–Sheinwold (or "K-S") bidding system was developed and popularized by Edgar Kaplan and Alfred Sheinwold during their partnership, which flourished during the 1950s and 1960s. K-S is one of many natural systems. The system was defi ...
(K–S) bidding system for the popular card game
bridge
A bridge is a structure built to span a physical obstacle (such as a body of water, valley, road, or rail) without blocking the way underneath. It is constructed for the purpose of providing passage over the obstacle, which is usually somethi ...
. The original structure of
Precision, another bidding system, also employed inverted minors over a 1 opening. However, the treatment is no longer restricted to users of these bidding systems. although partnerships that use a Short club system (where a 1 opener might only have 2 clubs) tend also to use the convention only after a 1 opener.
Description
The traditional approach in
Standard American
Standard American is a bidding system for the game of bridge widely used in North America and elsewhere. Owing to the popularization of the game by Charles Goren in the 1940s and 1950s, its early versions were sometimes referred to simply as 'G ...
and
Acol
Acol is the bridge bidding system that, according to '' The Official Encyclopedia of Bridge'', is "standard in British tournament play and widely used in other parts of the world". It is a natural system using four-card majors and, most commonly ...
, for example, is for a single raise of a minor suit opening to show a weak supporting hand and a double raise as showing a stronger hand of limit raise strength. Using the inverted minor treatment, a single raise of opener's minor suit is strong (usually at least 10
HCP) and a double raise is pre-emptive showing less than 7HCP (which leaves a small gap of 8-9 HCP where judgement is needed on whether to upgrade, downgrade or make a different bid).
The single or double raise promises at least five-card support for the minor. In the original version of K-S, and as further developed by Kaplan through the 1990s, both raises also deny a four-card major.
This typical (but minimum) single raise in clubs is taken from the system book:
[The Kaplan-Sheinwold System of Winning Bridge, Fleet Press Corporation, 1963.] 765 K84 A5 Q9652.
This is minimum for a double raise: 765 84 85 J97652. One might use it at favourable vulnerability only. In either case, the partnership is on solid ground after a single raise: opener is either unbalanced or strong, and responder has ''at least'' an average hand. The single raise leaves plenty of room to explore for the best contract, and even leaves room for an incautious opponent to enter the bidding and be penalized heavily.
This treatment is well suited to a bidding system that employs the weak no trump. With 1NT used for balanced hands in t