The 2NT response to the unbalanced 1♦ opening bid
In Modern American bidding, our 1♦ opening bid promises at least 4 diamonds and unspecified shortness. If we don't have a singleton or void, then we will have at least 6 diamonds. This can be awkward for responder when they hold a balanced 13-15 HCP. If they can't bid a 4-card major or raise diamonds (inverted, forcing bid), how do they know 3NT is the correct contract? Typically, opener has a 3154 shape hand. If responder doesn't have a 4-card major, opener's shortness in a major likely gives the opponents 9 cards in that major. 3NT may be doomed if opponents can run off 5 tricks in the major. However, opener isn't guaranteed to have shortness in a major. They may have a 6-card diamond suit and a 3-2-2 remaining shape; they could have opened a 4-4-4-1 hand. Additionally, the opener may have above-average values and will wonder if they can make a small slam. The crux is that jumping directly to 3NT closes out any chances to explore options toward a final contract.
In our responses to the Unbalanced 1♦, we defined the jump bid of 2♥ to show a flat, balanced hand with 11-12 HCP to invite to a game. That frees up 2NT for our purposes. We can use the 2NT bid to show the same shaped hand as 2♥, but with more points. 13-15 HCP. This bid is forcing for at least one round. Its purpose is to allow opener a vote in the 3NT game contract. Opener may be extremely wary of playing 3NT. Opener may also want to explore a small slam.
1♦ - 2NT: 13-15 HCP, denies a 4-card major, also denies a 4-card diamond suit
Responses: (2NT cannot be passed)
- 3NT - This game is acceptable to me.
- 3♣ - 5-5 in minors and minimal (11-12 HCP) opening hand
- 3
- 6 diamonds, no side shortness. Typical (11-14 HCP opening hand) - 3
/3
- 6 diamonds, this is my short suit (splinter). Decide if you want to play 3NT or 5♦ or try for small slam - 4♣ - 5-5 in minors and extra values (15+ HCP)
- 4 - 6 diamonds, slam values. This is Ace Asking (minorwood)
Once opener has chimed in with their hand, showing shape and strength, responder is in a good place to make a tactical decision on the ultimate contract.
When opener shows a minimal two-suited hand, responder may (likely) feel comfortable reaching a 5♣ contract. If opener responds with 3♦, responder with an Honor XX in diamonds and reasonable control in the side suits will bid 3NT expecting to run the 6 diamond tricks. Responding to opener's strong responses is even easier. If opener is exploring slam, responder only has to describe their hand. This usually means bidding their first-round control suit. Additionally, they can bid 4♦ as minorwood, ace asking. So much flexibility, so much power in not closing out the auction with a direct jump to 3NT.