Siege

1H/S = 5+ cards, Rule of 20

Responses to 1H -

1S = natural (won't have 3 hearts unless invitational+ or very weak)
1N = 5-11, non-forcing
2m = Game forcing
2H = 7-10 approx
2S = Invitational+ raise, usually balanced, asks for shortage
2N = Invitational+raise, usually unbalanced, asks for values
3m = 6+cards, invitational
3H = 3-8 approx, 4 card support
3S = any splinter, 3NT now asks
3N = void splinter in spades
4C/D = void splinter

Responses to 1S -
1N = 5-11, non-forcing
2C = GF except rebid
2D/H = Game forcing
2S = 7-10 approx
2N = Invitational+ raise, usually balanced, asks for shortage
3C = Invitational+raise, usually unbalanced, asks for values
3D/H = 6+cards, invitational
3S = 3-8 approx, 4 card support
3N = any splinter, now 4C asks
4C/D/H = void splinter

After 1H:1S:

• 1NT shows any 15+ (except for 5-5 GF hands)
• 2C natural, min (can be 2533)
• 2D 4+cards, min
• 2H 6+cards, min
• 2S 3+cards, min
• 3C 5+cards, GF
• 3D 5+cards, GF
• 3H 6H3S, GF
• 3S 4+cards, invitational

After 1H:1S, 1N -

• 2C shows 0-1 H, either weak or GF
• 2D shows 2+H, either weak or GF; or invitational with 6S2H
• 2H shows 2H, invitational (7-8 points approx).
• 2S shows 6S, 0-1H, invitational
• 2N shows 4-5S, 0-1H, no 6 card minor, invitational
• 3m shows a 6+ card suit, invitational

After responder's 2C rebid, opener assumes responder is weak and, unless GF values, bids accordingly:

• 2S with 3
• 2D with 4
• 3C with 5
• 2H with 6
• 2S with 2 (2524, 2533)
• 2D with 3 (1534)

Responder must now pass with the weak variant, except for after 1H:1S, 1N:2C, 2D, when a misfitting responder can bid 2H instead. Opener may look for a better part-score if he sees fit.

With GF values over a 2C response, opener bids

• 3D with 4
• 3S with 4
• 3H showing 6, looking for a singleton honour in partner's hand
• 2N Balanced or 4 clubs

After 1H:1S, 1N:2D, opener bids 2H without 3 spades, 2S with 3 spades, or higher to GF.

After 1H:1NT, 2m (3+cards), 2NT is invitational without support, 2S is invitational with 4+card support for opener's minor.

After 1H:2m, reverse's show extras, 3m does not. Jumps to game by responder are picture showing (1H:2C, 2H:4H = 2325 with an extra card somewhere, no ace or king in the outside suits)

After 1H:2S -

• 2N = Spade shortage
• 3C = Club shortage
• 3D = Diamond shortage
• 3H = no shortage, minimum
• 3S = no shortage, GF. Now step responses showing 9-11, 12-13, 14-15, 16-17
• 3N = 5-6 in majors
• 4m = natural, at least 5-5

After 1H:2N -

• 3C = Either values in clubs or any hand that does not wish to make a game-try. Now 3D asks which opener has (3H = minimum, higher = club game-try)
• 3D = Values in diamonds
• 3H = values in spades, non-forcing
• 3S = values in spades, GF. Now 3NT = Friv
• 3N = 5-6 in majors
• 4m = natural, at least 5-5