Byzantine Blackwood

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Constructed by Jack Marx. Named Byzantine because Byzantium came after Rome. There is no reason why the ask cannot be a bid other than 4NT (say 4C).

1. A KEY suit is:-
a] any suit bid and supported.
b] any suit bid by the partner of a NT opener.

2. A HALF-KEY suit is one which is bid but not supported and not 1b above.

3. Byzantine is not used if there are more than 2 key suits. (.
4. If there is only one key suit, we permit one half-key suit.

5. Queens only count when accompanied by their kings.
6. Step bid after response asks for other useful cards.
7. Resposes are:-
bid no. of key cards 1 key suit 2 key suits
--- ---------------- ---------- -----------
5C 0 or 3 0 aces 0 aces
3 aces 3 aces
2 aces+key K 2 aces+key king

5D 1 or 4 1 ace 1 ace
4 aces 4 aces
3 aces+key K 3 aces+key K

5H 2 aces or 3 key 2 aces 2 aces
cards AKQ of key suit AKQ of key suit
key AK+half-key K 1 ace+2 key K

5S 4 key cards 2 aces+key KQ 2 aces+key KQ
3 aces+half-key K 2 aces+2 key K
1 ace+key K +key KQ

5NT 5 key cards 3 aces+key KQ 3 aces+key KQ
4 aces+key K 4 aces+key K
3 aces+3 key K
2 aces+key KQ + key K
1 ace + key KQ +key KQ

6C 6 key cards 4 aces+key KQ 4 aces+key KQ
4 aces+half-key KQ 2 aces+key KQ +key KQ
4 aces+key K+half 4 aces+key K+key K
-key K
2 aces+key KQ
+half-key KQ