Byzantine Blackwood is a bidding convention in the game of bridge. Devised by Jack Marx, it is a complex version of the Blackwood convention (by which a four notrump (4NT) call asks about partner's honor card holdings). [1] Its premise is that both aces and kings may safely be shown in response to a Blackwood-type 4NT enquiry; provided that such kings are in well-defined key or half-key suits, there being no more than two such suits. [2] The name was chosen to express the idea that Byzantine Blackwood is a development from Roman Blackwood, by analogy with the Byzantine Empire and the Roman Empire; [3] rather than that the convention is of Byzantine [4] complexity. It seems to be little used nowadays (2014), most experts employing some form of Roman Key Card Blackwood.
Key suits are defined as:
A half-key suit is defined as a genuine suit that has been bid but not supported. When each partner has bid a half-key suit, the suit bid by the four notrump bidder is the half-key suit in which a king may be shown. Or use Blackwood or RKCB in this situation.
Byzantine is initiated by a call of 4NT and there are two scales of responses: one for use when there is only one key suit, and one when there are two. If there is only one key suit, the king of a half-key suit may be shown; if there are two key suits, half-key suits are not shown. The responses to 4NT are:
| Bid | With one key suit | With two key suits |
|---|---|---|
| 5♣ | 0A; 3A; or 2A+kK | 0A; 3A; or 2A+kK |
| 5♦ | 1A; 4A; or 3A+kK | 1A; 4A; or 3A+kK |
| 5♥ | 2A; A+kK+kQ; or kA+kK+hK | 2A; k(A+K+Q); or A+2kK |
| 5♠ | 2A+kK+kQ; or 3A+hK | 2A+k(K+Q); 2A+2kK; or A+kK+k(K+Q) |
| 5NT | 3A+kK+kQ; or 4A+kK | 3A+k(K+Q); 3A+2kK; 4A+kK; 2A+kK+k(K+Q); or A+2k(K+Q) |
A=ace, kA=key suit Ace, kK=key suit king, kQ=key suit queen, k(A+K+Q)=ace, king and queen of the same key suit, hK=half-key suit king
Thus, when there is only one key suit, a Byzantine 5♣ response shows either: no aces, three aces, or two aces plus the key-suit king. The response when there are two key suits is the same; but when the answer is, say, 5♥, the meaning depends upon the preceding bidding sequence:
| Opener | Responder |
|---|---|
| 1NT | 2♦* |
| 2♥ | 4NT |
| 5♥ |
If 2♦ is a Game Forcing Stayman or a 2♥ transfer, then 4NT agrees to hearts as trump and 5♥ shows two aces, or one ace and ♥KQ. As there is no half-key suit the third option is invalid.
| Opener | Responder |
|---|---|
| 1♥ | 1♠ |
| 3♠ | 4NT |
| 5♥ |
Here there is a key suit and one half-key suit. The 5♥ response shows any two aces; ♥AKQ; or any ace plus ♠K and ♥K.
Responses are given in the style of Roman Key Card Blackwood and may be based on a key-suit king instead of one of the aces normally shown. Key suits include: [5]
Byzantine Blackwood is not used when there are more than two key suits.
| Opener | Responder |
|---|---|
| 1♠ | 2♦ |
| 2♥ | 4NT |
| 5♥ |
Here there is a key suit (hearts, agreed by implication) and two half-key suits (spades and diamonds). So, according to partnership agreements, it is plain Blackwood showing two aces or RKCB showing two keycards without the queen of trumps.
Byzantine Blackwood is not used in the first round of bidding, i.e., 1♥ - 4NT, as responder may only be interested in aces. Partnership agreement is required on whether the 4NT call is Blackwood or RKCB. Many expert pairs employ a direct bid of 4NT as regular Blackwood, as recommended by Marty Bergen. [6]
Cuebidding may follow the response of four notrump. In addition, after a response to four notrump has been made, a bid of five notrump asks for additional high card features. A king or doubleton king-queen not already shown in response to four notrump counts as one feature; a guarded king-queen combination not already shown count as two features. The responses are:
In the partnership card game contract bridge, the Blackwood convention is a bidding convention developed by Easley Blackwood in 1933 and still widely used in the modern game. Its purpose is to enable the partnership to explore its possession of aces, kings and in some variants, the queen of trumps to judge whether a slam would be a feasible contract. The essence of the convention is the use of an artificial 4NT bid made under certain conditions to ask partner how many aces he has; responses by partner are made in step-wise fashion to indicate the number held.
Stayman is a bidding convention in the card game contract bridge. It is used by a partnership to find a 4-4 or 5-3 trump fit in a major suit after making a one notrump (1NT) opening bid and it has been adapted for use after a 2NT opening, a 1NT overcall, and many other natural notrump bids.
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Gerber is a contract bridge convention devised by William Konigsberger and Win Nye from Switzerland who published it in 1936; John Gerber of Texas introduced it to North America in 1938 where it was named after him. It is similar to Blackwood but uses 4♣ instead of 4NT as a relay (asking) bid to inquire about the number of aces held by partner. A further relay bid may follow to inquire about the number of kings held.
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