Inverted minors

The term inverted minors refers to a treatment used by the Kaplan-Sheinwold (K-S) bidding system (Precision, as originally structured, also used inverted minors over a 1Diams opening). Under this treatment, a single raise of opener's minor suit is strong (usually at least 9 HCP up to 20 HCP), and a double raise is pre-emptive, showing a maximum of 8 HCP. Thus, the treatment inverts the usual structure of the single raise as weak and the double raise as showing limit raise strength.

The single raise promises at least four card support for the minor, and the double raise promises at least five card support. In the original version of K-S, and as further developed by Kaplan through the 1990s, both raises denied a four card major.

This treatment is well suited to a bidding system that employs the weak notrump. With 1NT used for balanced hands in the 12-14 HCP range, responder to a 1Clubs or 1Diams opening knows that partner has either a good hand, 15-17 balanced, or an unbalanced hand with genuine length in minor suit. If opener has a three-card minor, he most often has a strong notrump hand; then, if desirable, it's easy to veer into notrump following the single raise.

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.

After a double raise, the partnership seldom bids on. The idea, of course, is to pre-empt the opponents and cause them to miss their best contract. The exception occurs when opener has a very strong hand, perhaps one with which he intended to jump in notrump at his second turn (showing 18-20 HCP in K-S). That hand might simply bid 3NT after the double raise, but the decision can be a difficult one: it's opener, not the opponents, who has been pre-empted. Many players, holding a 19 HCP balanced hand, would continue to 3NT over a double raise only when vulnerable at IMPs.

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.] : Spades 765 Hearts K84 Diams A5 Clubs Q9652.

This is minimum for a double raise: Spades 765 Hearts 84 Diams85 ClubsJ97652. One might use it at favorable vulnerability only.

References

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