2♣ Opening

♥ ♣ ♦ ♠

When to open 2♣?

(i) Any balanced hand with 23+ HCP.
(ii) Any unbalanced hand with a strictly counted LTC with a strict maximum loser count of 3.5 LTC.
(iii) Exclusions: Any 2-suited hand 5-5 or better. See 55+ for their treatment.(2♣ sequences are not available for 2-suited hands)

The aim of the initial response is to indicate presence of Key Cards, simply: Aces & Kings by calculating a total of 'Italian controls'

Produce your total of Italian control count by counting TWO for each Ace and ONE for each King held

Partner's response of 2♥, if intervention * or ** indicates 1|2 - count: 1.5
Partner's response of 2♠, or next suit after intervention indicates 3|4 - count 3.5
Partner's response of 2N, or next suit+1 after intervention indicates 5|6 - count 5.5
For 2♦ or any other response - break-outs - the count is ZERO.
Add the partner's count to your own and subtract the total from 12. This deduces a rough upper estimate of your combined LTC!

Consider that a NT or Major game is likely if total LTC is <= 4 and a slam could be on the cards if <= 2.

This of course has not taken into account key distributional information, a fit for a trump suit or how the hands fit together.
Subsequent questions are now asked by the 2♣ bidder to ascertain relevant key suit and control requests provide for pin-pointing key trump support and key distributional information.

Initial inquiry is made in a potential trump suit or in a key secondary suit if primary is solid. Or if considering playing in NT's investigate a key suit where help is required to develop tricks or to complete an adequate guard.
The earliest decision to be made has to be whether to pursue contractiong in a suit or in NT's. Balanced hands often lean towards a NT contract - or if intending a suit contract a suitable trump suit fit.
Also 3NT needs to be decided rapidly - quickly as biing space is limited. Next a decision if a slam is possible or out of the question.
Then other suits can be inquired for controls to decide whether there is any slam prospect or not
The LTC count is then refined later on following a 4NT request when the precise number of missing Aces & Kings is determined (and probably their location has become known through other inquiries)

If partners initial response is negative - 0 controls - initial prospects depend only on his own hands's trick taking power but awareness of a lack of ready entry to partner's hand has already become evident.
If partners response is positive then entries are likely to be available and give further help in developing the play of the hand

The first suit inquiry is usually made in declarer candidate trump suit or side suit (usually best if main suit is fairly 'standalone'.
The second or further inquiries can be a request in a second suit checking for length or controls.
Any further request is a further control request.
Initially A's And K's was the objective, answer's to subsequent requests also involve the Queen & length & placement of controls.

There are 2 types of Negative responses (0 controls)

a) Initial break-out responses an encouraged alternative when habing a negative response BUT a long side suit when only if other response is a negative (1st step response).
3any    Steps 5-8 No A|K, any 7 card suit OR a 6 card suit headed by Q. This is termed a 'Break-out'.
                      E.g:   2♣ - 3♦ : shows a break-out in Diamonds. The 2♣ bidder will seriously consider the use of a                    Break-out suit as a potential trump suit as otherwise of very little use.
2♦          Step 1: Neither A|K and No break-out suit available

Positive responses-steps 2, 3 & 4

2♥                Either 1 Ace OR 1or2 Kings (That's: 1 or 2 italian controls)
2♠                Either 2 Aces OR 1 Ace & 1 or 2 Kings OR No Aces but 3 or 4 Kings (That's: 3 or 4 italian controls)
2NT              5+ controls. (That's 5|6 or more italian controls)
                        7+, can it really happen? responder may need to correct the level of the final contract bid by your partner     who may not become aware of at least one critical control....

Queens are ignored in the initial response. However their presence is literally pivotal in Break-outs and in all subsequent responses to requests to Trump & Control requests.

If intervention precedes responder's response then your 4 steps are modified as follows:

PASS : shows a negative e.g 2♦ response - no worry partner gets another bid!
*|** : shows a normal 2♥ response 1-2 controls
Next suit : shows a normal 2♠ response 3-4 controls
Next+1 suit : shows a normal 2N response 5+ controls

Notes:

As is the custom throughout responder partner always includes NT bids in his step responses.
E.g. 2♣-2♥(intervention)- steps would be (P * 2♠ 2N) thus the 4th step 5+ Controls would be 2N as usual & 3♣...3♠ shows breakouts ♣..♠ as usual...
Only an interventions of 2♠ or above, alters displaced responses breakouts: In the case of 2♠ then breakouts are:: 3♦ 3♥ 3♠ 3N(clubs). Alternatively by agreement is to ignore possiblility of a break-out in the opponents suit and use it instead of any 'displaced' gehuine break-out!
Interventions of 3mi may cause some difficulties...however opponents are taking a sgnificant risk of a heavy penalty. But if responder has a Breakout we strongly recommend that it is shown excet of in the opponents suit - as likely to have length!

Also interferences have shown in practice to aid declarer more and not disturbing our 2C sequences significantly.

2♣ bidder's rebid following a negative response 2♦ or break-out or PASS following any intervention:

Balanced Hands: natural 2NT 23-24HCP or 3NT limit bids 25+ HCP. Note closure in 2N is not possible over any other initial response.
Unbalanced: make a trump request in a 5+ card suit or even in a secondary 3+ card suit when holding a solid main suit. With 2 suits: Rule1: ignore a solid suit for 1st inquiry, Rule 2: conserve bidding space - both of these are important. Note: If partner has responded to 2♣ in your suit, then 2NT, saving bidding space, is a trump request in his partners suit. E.g. 2♣-2♥-2N is a trump request in Hearts! & 2♣-2♠-2N is a trump request in Spades.
The so called trump request is still valuable when aiming at NT slams - allowing a request in a critical suit. E.g. in a short suit requiring help. Etc.
If partner made a break-out you may have choice of playing in the breakout suit or possibly in NT's UNLESS you hold a solid suit.:- make up your mind! Note: trump requests are not used over a 'break-out' see further on

2♣ bidder's rebid following a positive response (steps 2,3 or 4) - following options are available:-

make a natural 3NT bid to play - usually denies a 5 card suit. However over an initial 4th step 3N is forcing to slam and asks partner to show his suit with the highest LTC count.
make a King request by 4NT 25+ HCP, denies a 5 card suit. A 5NT rebid is then non-forcing.
make a trump request by normally bidding a 5+ card suit. NOTE: if responder bid 2♥ or 2♠ or (possibly 3♣ 4th step following a 2♠ intervention) - then a 2NT bid is a trump request in responder's reply suit. See below, if opponent intervene before you (-1:PASS is lower suit,-2:*|** is opposite suit, +1:Next). Responder with a negative response may bid +1 OR a breakout (step 5 and onwards) in any 6+ card suit or 5 card suit headed by a Q.
Even if balanced and intending ONLY a NT contract, one may make a trump request in a 4 or even in a 3 card 'side' suit.

Note: If responder has declared 5+ controls by bidding the 4th step, then it is slam forcing: Usual choice will be whether to play 6N or 7N!

The 2♣ opener still remains totally in charge even if partner makes a break-out. The theory is that with a strong hand facing a weak hand is that a Question-Answer approach makes most sense - making responder totally subservient! However if opener attempts to close at the 5 or 6 level, the responder, with a GOOD reason opener is not aware of, may proceed up a level to 6 or 7! ~ BUT MAY NEVER CHANGE THE DENOMINATION CHOSEN.

Options for continuation after a break-out response to 2C opening or a subsequent suit request:

Break-out suit request - next suit - not a cntrl request: all others bids are cntrl requests except 3N to play

1st step NO Queen
2nd step 6 cards with Q
3rd step 7 cards with Q
4th step 8+ cards with Q

3NT To play (rare - on 9 tricks in hand) - confident to run the break-out suit
4NT For Queens. However If partner has shown no Aces or Kings! i.e. 0,1,2,3|4 (same style as for kings); otherwise if partner made an initial positive response then 4NT asks for Kings - as usual!

Two possible uses can be made of these length requests.
A) If declarer considers to play in his suit he may check the length partner holds
B) If declarer is considering playing in the breakout suit it can be used to determine if critical losers are covered by shortages in his partner's hand

Note: Assuming a 7 card suit - likely distributions are 7222, 7321, 7330, 7420, 7411.
Note: if the required step response reaches or exceeds 4NT THEN response must be the normal response to a 4N request (either forK's or Q's)

How 2♣ bidder handles RHO intervention

(A) If partner had made a normal step response (i.e when he did not receive prior intervention)
Opener rebids as follows:

PASS Shows a request in the suit below opponents bid (-1)
**|* Shows a request in the non-touching partner's suit (-2)
Next_bid This bid is ALWAYS natural!

Ex1: 2♣-2♥-(2♠ opponent) then:
PASS = Heart trump request (suit - 1) 2N also has the same meaning.
* = Diamonds TR REQ (suit -2)
3♣ = Clubs TR REQ (Next bid: Natural)
3NT = To play. Natural

Ex2: 2♣-2♠-(* opponent) then:
PASS = Heart trump request (suit -1)
2NT = Spade trump request - Space saving (unusual in this sequence! but possible)
** = Diamond trump request (suit-2)
3♣ = Club trump request (Next suit -Natural)
3NT = To play.

Ex3: 2♣-2♥-(3♣ opponent) then:
PASS = Spade TR REQ (suit-1)
* = Heart TR REQ (suit-2)
3♦ = Natural Diamond TR REQ (suit+1)
3NT = To Play

(B) If partner made a positive response after intervention & RHO Passes
Note1: NT bids are always included in responder's steps.
Note2: If RHO bids too see above
Partner has bid PASS, */**, +1, +2 (PASS is negative 1st Step)

Ex 1: 2♣-2H(opp)-2♠-PASS(opp) Then partner has shown 3-4 controls (3rd step):
2NT = partner's response suit : TR REQ in Spades
3NT = To Play
PASS = ILLEGAL? only if wanting to play in 2♠ - UNLIKELY
* = ILLEGAL!
3♣ = Clubs TR REQ (+1 Natural)
3♦ = Diamonds TR REQ (+2 Natural)

Ex 2: 2♣-*(opp)-**-PASS(opp) Then partner has shown 1-2 controls (2nd step) Then:
2♦|♥|♠ are trump requests
2N is a trump request in Clubs (Not usual if opponents double showed Clubs)!
3NT is to play

Ex3. 2♣-2H(opp)-PASS-PASS(opp) Then partner has shown 0 controls (1st step) Then:
Both 2NT & 3NT are to play (as usual over a negative response)
* is a trump request in Hearts (rare - space saving bid for Hearts if overcall is not showing Hearts!)
2♠, 3♣ & 3♦ Are trump requests as usual

4NT may also be used for Kings (positive responses) or Queens (step 1, negative) as the case may be
Jump control requests may be made too

Following a Trump request and an initial negative response (1st step) 2♣ bidder now has 3 options:
(i) Bid 3NT's to play, if available.
(ii) Deleted -no longer played as a 2nd trump request. A Rebid in a new suit is now a control request - see below.
(iii) Rebid in his TR request suit is always a 'length' request. This can be used to show a long suit in a single suited hand.
(iv) Make a control request in any NEW suit.
(v) Bid 4NT for Queens [responder has previously declared no Aces or Kings]

Following a trump request and a positive response (2-4steps) 2♣ bidder has these options:
(i) Make a control request usually in the suit with highest LTC. (Note: 3NT is no longer natural and can now used to save bidding space for a cntrl request in partner's previous step response!)
(ii) Bid 4NT for kings
(iii) Rebid his trump suit at any level
Note: The trump suit is usually set by a positive trump response - but other contracts can be selected by the 2♣ bidder at the slam level - partner must not 'correct' to the previously apparently agreed suit - remember the 2♣ bidder is responsible for the final denomination. There is a small leeway for a responder to bid 7 over 6 or 6 over 5 with good reason.

Following a negative response to a 2nd Trump Request
3NT: To Play
4NT: For Kings (Queens if a negative initial response)
New suit (any level): To Play

Following a control request and a negative response (1st step) 2

bidder has the following options:
(i) Make a further control request Note: one can be made if their is bidding room for at least 1 step short of 4NT. For example 4♥ is highest possible control request with a 4

negative response and 5♣, 5♦ etc showing 0, 1 etc Kings AS IF 4NT had been requested AND also implying the 2nd step or possible better to the 4♥ request or 3rd step or possibly better to a 4♦ request.
(ii) Bid 4NT for kings (Queens if a negative initial response or initial breakout)
(iii) Rebid his trump suit at game or higher level to play
(iv) Rebid his suit below game is a 'length' request. 2-steps only

Top honour A|K|Q e.g Kx
Otherwise xxx

Further Examples!

Ex1 A straightforward slam?
AJ8                      6
AKQ74               T653
AQ                      KJ32
KQ6                    9543

2♣                       2♥ (POS: 1 control K♦)
2N(♥ tr req)       3♥ (POS: 3rd step): Qxx...Jxxx inclusive - a certain entry
3♠(♠ cr req)         4♣ (2nd step: 2nd round Spadecontrol: KS or singleton)
4♦(♦ cr req)       4♠ (2nd step: 2nd round Diamond control: KS or singleton)
6H   Worth a shot!

Ex2: more complicated! (note deductions)

A2                        K
96                         AKT872
KJT93                   8
9732                     AKQJ6

P 2♣
2♠(3|4 cntrls)    3♥(tr req) P showed an A+ K or 2 Aces or A+2K's - now makes a trump request in Hearts.
3♠(neg) 4♣ (cntrl req) P showed <Jx in Hearts - so AK lie outside of Hearts also P has not a 6 card suit (he would break out if he had)
4♦(neg) 4N              P deduces at least xxx in clubs & asks for number of Kings held
5♦                           6♣             Partner shows one King (therefore also one ce): Its only a 50% slam but should be bid
No real need to ask 4N! as it commits you to 6♣ - cannot risk 6♥ as P may have only a singleton
Partner has either A♠|♦ & K♦ or both Aces

Note1: one can ask a length request in a potential trump suit announced with a trump request
Note2: it would be a mistake to make a trump request in Spades (a stand alone suit)

But we prefer a 3♦ opening with such 2-major suit hands:
3♦! *(opp) 3N! (2 or more key cards)
4♥!                  4N! (4♥: shows 6-5 or better and void in clubs) :4N inquires for LTC
6♥                Partner does not reply! and instead closes in 6♥. Usual Heart distributions are 7222 or 7321 or 7330 or bad luck 7411 or 7420...

A better contract than 6♥!