BYZANTINE
BLACKWOOD

Ever since Mr. Easley Blackwood created his concept of Ace-Asking for slam attempts, several variations on this theme have popped up. One of those variations is a complex variation devised by Mr. J.C.H. Marx of Great Britain. The responder responds to 4 No Trump in a similar style to Roman Blackwood, in that a Key Suit King is shown instead of one of the Aces.

It must be noted that Byzantine Blackwood has no application if there is more than one Key-Card Suit. If there is only one Key-Suit, a King of a Half-Key Suit may be shown, which indicates a genuine suit that has been bid by not supported.

It also must be noted that Byzantine Blackwood is never initiated on the first round of the Auction. If 4 No Trump is initiated on the first round of the auction, then this becomes and is treated as the Blackwood convention in all its forms.

The complexity of Byzantine Blackwood derives from the fact that there are two different forms of responses and their interpretations. The first form is applied when there is only one Key Suit, and the second form is applied when there are two Key Suits.

Key Suits are:
1. An agreed upon Trump suit
2. Any genuine suit bid and supported by partner
3. Any suit bid by partner and responder bids No Trump. For example, if partner bids 1 Spade and responder bids 2 No Trump, then Spades becomes the Key Suit.

According to Mr. J.C.H. Marx, if there is only one Key Suit, then the responses to 4 No Trump are as follows:

Responder	Meaning
5	0 or 3 Aces	or	2 Aces and Key Suit King
5	1 or 4 Aces	or	3 Aces and Key Suit King
5	2 Aces	or	2 Aces
		or	Key Suit Ace/King/Queen
		or	Key Suit Ace/King plus the King of the Half-Key Suit
5	2 Aces	or	3 Aces plus the King of the Half-Key Suit
	plus the Key
	Suit King/Queen
5 NT	3 Aces	or	2 or 4 Aces plus the King of a Half-Key Suit
	plus the Key
	Suit King/Queen

According to Mr. J.C.H. Marx, if there are two Key Suits, then the responses to 4 No Trump are as follows.
It must be noted that Half-Key Suits are ignored if there are two Key Suits.

Responder	Meaning
5	0 or 3 Aces	or	2 Aces and Key Suit King
5	1 or 4 Aces	or	3 Aces and Key Suit King
5	2 Aces	or	Key Suit Ace/King/Queen
		or	1 Ace and both Key Suit Kings
5	2 Aces	or	2 Aces plus the Key Suit King/Queen
	plus the Key	or	2 Aces and both Key Suit Kings
	Suit King/Queen	or	1 Ace plus the Key Suit King/Queen of the Second Key Suit
5 NT	3 Aces	or	3 Aces and both Key Suit Kings
	plus the Key	or	4 Aces plus one Key Suit King
	Suit King/Queen	or	2 Aces plus the Key Suit King of one Key Suit
			and the Key Suit King/Queen of second Key Suit
		or	1 Ace and the Key Suit Kings/Queens of both Key Suits

After the first response to Byzantine Blackwood, cuebidding may follow. A bid of 5 No Trump after the first response asks for a high card Feature. For example, a King or a King/Queen combination not already shown in the response is counted as one Feature. A second King/Queen combination not already shown in the first response counts as a second Feature. The responses to 5 No Trump are as follows:

6	shows	0 or 3 Features
6	shows	1 or 4 Features
6	shows	2 Features

Mr. J.C.H. Marx devised a most complex conventional method which has its advantages and disadvantages. The most single disadvantage is that memorization of the guidelines is essential and prior practice with an experienced partner is absolutely necessary. If you wish to make the Byzantine Blackwood a part of your Partnership Agreement, we urge you to honor these two factors. If you discover that Byzantine Blackwood fits your Partnership Agreement, then it should be included, and it should also be made known to your opponents at the Bridge Table by writing it in the appropriate place on the Convention Card.

If you wish to include this feature, or any other feature, of the game of bridge in your partnership agreement, then please make certain that the concept is understood by both partners. Be aware whether or not the feature is alertable or not and whether an announcement should or must be made. Check with the governing body and/or the bridge district and/or the bridge unit prior to the game to establish the guidelines applied. Please include the particular feature on your convention card in order that your opponents are also aware of this feature during the bidding process, since this information must be made known to them according to the Laws of Duplicate Contract Bridge. We do not always include the procedure regarding Alerts and/or Announcements, since these regulations are changed and revised during time by the governing body. It is our intention only to present the information as concisely and as accurately as possible.