Siege

Any GF, 22-24 bal, or a weak 2 in diamonds (6 cards 1st vul/2nd, may be 5/4 or 5/5 minors 1st NV)

Responses -

• 2D Waiting, to play opposite weak 2D
• 2H enquiry, looking for game opposite weak 2D
• 2S natural NF. Any weak hand with 3 spades raises, with 0-1 spades passes.
  
• 2NT Hearts, forcing
  
• 3C Semi-positive or better in diamonds (now 5D = weak two, others = strong)
• 3D = preemptive, guessing that partner has the weak two.
• 3H = mildly invitational opposite a weak two
  
• 3S = strongly invitational opposite a weak two
  

We used to play that 2D was a semi-positive and 2M to play, either natural positive or artificial double-negative. This was fine until we felt the need to investigate a 4M contract opposite a weak two!

Over a 2H enquiry -
2S = any min, or a max without shortage (will bid on). Now 2N/3D = NF, others GF
2N = Any strong hand, forcing to slam; now 3C = waiting, others = nat
3C = max, naturalish (after a 1st NV opening, this is likely to bid iff opener has only 5 diamonds)
3D = max, club shortage
3H = max, spade shortage
3S = max, heart shortage (now 4S = to play)
3N = max, balancedish, keen to declare (now 4S = to play)

Over 2S -
2N = max, two spades - now 3D NF asking for 2 top honours in D, 3C/H nat game-try
3C = min, three spades - now 3D/3H game-tries

Over 2N -
3C/D/H nat NF (3C may be on a good 3 card fragment, 3H may be on a doubleton)
3S = max, typically 2 hearts
3N = max, typically 0-1 hearts

Over 3C -
3D = GF hand, waiting
4D = GF hand, sets diamonds
others = nat

If 2C is doubled, pass is a suggestion to play; Opener is typically expected to correct with 5D2C or 6D3C 1st NV; 6D2C is borderline in other positions.

After an overcall, assume opener has the weak option - double is pens, new suits are constructive, NF. Doubling a diamond bid is lead-directing.

Over 2C:2D, standard stuff when opener is strong; 2H Kokish includes 22-24 balanced.