Earlier we mentioned that the 1♦ opening is vague, defined by what it is not rather than showing specific characteristics. (No 5-card major, not preemptive, not appropriate for 1NT, and fewer than 16 HCP.)
After playing for a while, we found that its completely artificial nature (not promising any diamonds at all) made it hard for Responder to distinguish between hands with length in one minor and hands with length in both minors. In a typical auction such as 1♦–1M–2♣, there's just no way to tell if Opener has 6 clubs or is 5-4 in the minors. And that makes finding the proper partscore extremely difficult.
We soon realized, however, that whenever Opener has length in both minors (meaning at least 5-4), the auction nearly always proceeds: 1♦–1X–2♣. So we decided to cut to the chase and just open those hands with 2♣.
The reasoning is very similar to one benefit of opening a weak notrump: Instead of starting with 1m and making a rebid that properly describes your hand, just start with the descriptive bid.
Since we still hate searching for 4-4 major fits at the 2-level, opening 2♣ also denies a 4-card major.
- More preemptive. Opening at the 2-level makes it harder for opponents to interfere.
- More descriptive to partner. Responder often knows immediately where the best fit is.
- Less descriptive to opponents. Responder doesn't need to bid a 4-card major.
Responding to 2♣
With no interest in game or slam, Responder should attempt to place the contract. This can mean passing 2♣ or bidding 2M, 3m, 3NT, 4M, or 5m. (Opener is expected to pass these bids.)
With invitational values but no 5-card major, Responder can invite with 2NT or 4m.
With invitational values and a 5-card major (or with minor-suit slam interest), Responder starts with the artificial forcing bid of 2♦. Opener will then detail shape and strength. (As always, see the Eastern Mysticism Outline for details.)