Kroll: 3♣ Limit Raise with Exactly Three Trumps

Kroll is a compact 2/1 Game Force tool for an awkward major-suit-raise problem: responder has invitational values and exactly three-card support.

The convention is named after Dan Kroll, who plays in the Quicktricks Bridge Club in San Francisco, California. In a 2/1 partnership that plays Kroll, the auction starts with an uninterrupted 1♥ or 1♠ opening, then responder bids 3♣ artificially.

One practical benefit is that Kroll takes the three-card invitational raise out of responder’s 1NT response. That lets the partnership play responder’s 1NT as semi-forcing rather than fully forcing, because opener no longer has to cater to this specific limit-raise hand type hiding inside 1NT. Another benefit is that it shows responder’s hand right away, allowing opener to evaluate the partnership’s chances for game or slam, which is particularly helpful where the opponents would have interfered if responder were to start with 1NT forcing or semi-forcing.

The Basic Agreement

After partner opens one of a major and there is no interference:

1♥  3♣

or

1♠  3♣

Responder’s 3♣ is Kroll. It shows:

• Limit-raise strength, roughly 10-12 support points
• Exactly three cards in opener’s major
• Nothing about clubs

That last point matters. 3♣ is artificial and alertable. It says, “Partner, I have an invitational major suit raise but with only three trumps.”

Why Kroll Exists

2/1 Game Force methods leave three-card invitational raises a little clumsy.

A direct jump raise, such as 1♠-3♠, generally promises four-card support. Bergen-style methods also use 3♣ or 3♦ for major suit four-card raises. Jacoby 2NT is too strong, because it is game-forcing. A simple raise to 2♠ can undersell a good 10-12count. Starting with 1NT is possible in some methods, but that pushes an invitational raise into a bid many 2/1 pairs want to treat as semi-forcing.

Kroll gives the partnership one exact box for this hand type: invitational, major-suit support, exactly three trumps. With that box available, responder’s 1NT can stay semi-forcing and does not need to carry this hand.

Opener’s 3♦ Ask

After Kroll, opener can bid 3♦ as an asking bid:

1♠  3♣
3♦  ?

Responder now clarifies the hand.

Responder’s Rebids After 3♦

Responder has three kinds of answers.

Three of the Major: I Do Not Like My Hand

1♠  3♣
3♦  3♠

Bidding three of opener’s major says the hand is on the low side. Responder still has the promised limit raise with exactly three trumps, but the hand does not have extras.

Typical reasons to bid three of the major:

• Minimum values for the range
• Scattered queens and jacks
• No useful shortness
• Poor controls
• Soft values in side suits

Four of the Major: I Like My Hand

1♥  3♣
3♦  4♥

Bidding game says responder likes the hand. The values are still invitational rather than game-forcing in the original description, but opposite opener’s interest, responder is happy to accept.

Typical reasons to bid game:

• Maximum values for the range
• Strong trumps for only three-card support
• Aces and kings rather than queens and jacks
• Useful shortness

Any Other Suit: Natural (if Major) or Control

If responder bids a suit other than opener’s major, this is a matter of partnership agreement. It is useful to play that three of the unbid major is natural, probing for a 4-4 fit, as that fit often plays better than the 5-3 fit in the original major. It is also useful to play that any other new suit shows a control in that suit with a maximum invitational raise and good controls. Whether it shows a first-round or possibly second-round control depends on partnership agreement. Many pairs use Italian-style cue bidding: ace, king, void, or singleton.

Examples:

1♠  3♣
3♦  3♥

Responder shows a 4-card heart suit or heart control, depending on partnership agreement.

1♥  3♣
3♦  3♠

Responder shows a 4-card spade suit or spade control, depending on partnership agreement.

1♠  3♣
3♦  4♣

Responder shows a club control. The original 3♣ was artificial, so this later 4♣ is not showing a club suit. It is a control bid.

Opener’s 3 Major or 4 Major Signoff

After Kroll, opener can also bid 3 or 4 of our major as a signoff:

1♠  3♣
3♠

This is a signoff, saying opener has a minimum hand that is unlikely to make game across from a 3-card limit raise.

1♠  3♣
4♠

This is also a signoff, saying opener thinks we can make game but has no slam interest.

Opener’s 3 of the Unbid Major

After Kroll, opener can also bid 3 of the unbid major:

1♠  3♣
3♥

A good treatment is that this is natural, probing for a 4-4 fit in the unbid major, which often plays better than a 5-3 major fit. After that, responder can raise the new major with 4-card support or return to 3 or 4 of our original major.

Example Hand

Partner opens 1♠ and you hold:

♠ K 8 4
♥ A 7 5
♦ Q 9 6 2
♣ J 8 3

You have 10 high-card points, exactly three spades, and enough support to invite game. If Kroll is on, bid 3♣.

If partner asks with 3♦, you bid 3♠. The hand is minimum, flat, and full of soft values. You made your invitation, and opener can still continue with extras.

Now change the hand slightly:

♠ K Q 4
♥ A 7 5 2
♦ 9 6 2
♣ K 8 3

Same 12 high-card points, exactly three spades, but much better controls and trump texture. After 1♠-3♣-3♦, bid 3♥ to show a 4-card heart suit or heart control, depending on partnership agreement.

Kroll Compared with Bergen Raises

Kroll and Bergen Raises both use artificial 3-level responses after a one-major opening, so partnership clarity is essential.

A common Bergen structure is:

• 3♣: Constructive raise with four-card support
• 3♦: Limit raise with four-card support
• 3 of the major: Weak/preemptive raise

Kroll changes the meaning of 3♣. Instead of showing a constructive four-card raise, it shows exactly three-card support and invitational values. With the constructive raise, responder simply raises to 2 of the major, which leaves room for whatever game-try bids the partnership employs.

Alerting and Partnership Notes

Kroll is artificial and must be alerted. Do not assume opponents will understand that 3♣ is not clubs.

Agree on these details before using it:

• Whether the range is 10-12 high-card points or 10-12 support points
• Whether a new suit bid after 3♦ shows a natural suit (if 3 of the unbid major) or a control, and if a control whether first-round only or first- or second-round
• What direct three-of-the-major means when Kroll is available
• Whether responder’s 1NT over one of a major is forcing or semi-forcing when Kroll is available
• Whether Kroll is off by a passed hand (the inventor recommends Drury instead of Kroll by a passed hand)
• Whether Kroll is off after a double or overcall (the inventor recommends “on” after a double but “off” after an overcall, as a cue-bid is available)

Bottom Line

Kroll gives responder a clean way to say: “I have a limit raise, but exactly three trumps.” Opener can place the contract or investigate game or slam with 3♦.

It is a small convention, but that is the point. It names one common hand type accurately, and it keeps your major-suit raises from blurring three-card and four-card support.