Double check

In chess, a double check is a check delivered by two pieces simultaneously. In chess notation, it is almost always represented the same way as a single check ("+"), but is sometimes symbolized by "++" (however, "++" is also sometimes used to denote checkmate).

Discussion

The most common form of double check involves one piece moving to deliver check and revealing a discovered check at the same time from a piece it had been blocking. (Such a check is an inherent part of the type of smothered mate known as Philidor's legacy.) The only possible replies to a double check are king moves, as both checking pieces cannot be captured or blocked at once. In some cases, the king can capture one checking piece and escape the other in a single move.

In exceptional circumstances, it is possible for the moved piece to not participate in the double check (i.e. to give a "double discovered check", though this name is not actually used). The only way for this to happen in orthodox chess is by way of an en passant capture. In the position shown at right, Black has just played 1...g7–g5. White replies 2.hxg6e.p.++. The result is a double check even though the pawn White moved does not give check. (One check is given by the rook, discovered by the capturing pawn's move; the other by the bishop, discovered by the captured pawn's removal.) Such a double check is extremely rare in practical play, but is sometimes found in problems.

Double Check

Double Check is a 1982 sculpture by John Seward Johnson II, located in Zuccotti Park in Manhattan, New York City.

References

External links

Traces series

Traces is a series of novels written by author Malcolm Rose, about the adventures of Forensic Investigator Luke Harding and his Mobile Aid To Law And Crime, Malc. The first book, Framed!, has been selected by the United States Board on Books for Young People and the Children's Book Council as an Outstanding International Book for 2006.

Six books of the series were published between 2005 and 2007 by Kingfisher Books in the UK and by Turtleback Books in the US. All six books, plus a seventh, Murder Club (2013), have since been published by the author on Amazon Kindle.

Alternate England

The Traces universe is explicitly located in a future England, where the decayed and semi-abandoned South is supported and feared by the vibrant, successful North.