Muiderberg convention

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The Muiderberg convention in the card game bridge is also known as the Dutch Two opening. It is a two-level preemptive opening based on a two-suiter with precisely a five-card major and a minor suit (four-card or longer). In Muiderberg the 2 opening denotes five hearts and an unknown minor suit, whilst 2 denotes five spades and an unknown minor suit.

The convention is named after the Dutch village Muiderberg, the residence of the designers of this two-level opening (Onno Janssens and Willem Boegem).

System[edit]

The partner of the Muiderberg opener can take the following actions:

  • pass (with tolerance for the opened suit)
  • bid 3 (a pass-or-correct bid)
  • bid 3 to invite for game in the major suit
  • bid 2 (over 2) as a contract improvement (opener is allowed to raise with a suitable hand)
  • bid 3/ (opener's suit) as a preemptive raise
  • bid 3/ (other major) which is non-forcing but invitational
  • ask for the minor suit using a 2NT relay bid with a strong hand.

The 2NT response is often defined as forcing to game, for example in Biedermeijer and AcolPlus. In particular, with a strong hand with an own suit, responder must bid 2NT first as there is no other way to establish a force. The Muiderberg opener can respond in several ways to the 2NT answer:

  • bid 3 with a minimum and clubs / with a four clubs
  • bid 3 with a minimum and diamonds / with a four diamonds
  • bid 3 with a maximum and clubs / with a five or more clubs
  • bid 3 with a maximum and diamonds / with a five or more diamonds
  • bid 3NT with 4-4 in both minors
  • bid 4/ with a 6+ cards in the bid suit

Both approaches are equally popular.

In competition, 3 is natural (opener is expected to pass) while 2NT asks for opener's minor suit and is not necessarily strong. Further, 4/ are defined as fit-bids in competition.

Variants[edit]

A variant known as Lucas two-bids allow for 5 cards or more in the bid suit (diamonds, hearts or spades) and 4 cards or more in a second suit which can be any of the remaining three suits.