Қос шабуыл: шахматтағы екі бірдей қауіп

Chess term; a check delivered by two pieces simultaneously

In chess and other related games, 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 "++". (The symbol "++", however, is also sometimes used to denote checkmate.) This article uses "++" for double check and "#" for checkmate.

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. The only possible reply to a double check is a king move, as it is impossible to block or capture both checking pieces at once. In exceptional circumstances, it is possible for the moved piece in a double check to not give check. The only way for this to happen in orthodox chess is by way of an en passant capture. In the position shown from Gundersen–Faul, 1928, Black has just played 14 g7–g5. White replies 15. hxg6 #. The result is a double check even though the white pawn does not give check: one check is given by the rook, discovered by the capturing pawn's move; the other by the bishop, revealed by the captured pawn's removal. Such a double check is extremely rare in practical play, but it is sometimes found in chess problems.

A double check is a part of the smothered mate pattern known as Philidor's legacy. Aron Nimzowitsch wrote, "Even the laziest king flees wildly in the face of a double check." Because the only possible response to a double check is a king move, the double check is often an important tactical motif. A double check was also seen in the celebrated Evergreen Game, Anderssen–Dufresne, 1852. Anderssen won with:
20. Rxe7+! Nxe7 21. Qxd7+!! A queen sacrifice to set up a deadly double check. 21 Kxd7 22. Bf5++ Ke8
Or 22 Kc6 23. Bd7#. 23. Bd7+ Kf8 24. Bxe7#

In chess with variant rules or fairy pieces, other ways of delivering a double check may be possible. Triple, quadruple and even quintuple checks may also be possible. For example, in the position shown to the left, after Black plays 1 d5 to remove the check from the bishop on c4, White plays 2. exd6e. p.+++++. After the en passant capture, five pieces check the black king: both moas (the moa is a non leaping knight which first takes a diagonal step, then an orthogonal one), the rook, the grasshopper (the grasshopper captures by leaping over an intervening piece) and the bishop. Black would now be obliged to escape the check and play one of either 2 Kxd6, to recapture the white pawn right away, or passively evade the checks from the grasshopper and the bishop by playing 2 Kd7 or 2 Kf6. Another example is shown with the position shown on the right, after Black plays 1 e5 to remove the check from the nightrider on d3, White plays 2. fxe6e. p.+++. After the en passant capture, three pieces check the black king: the pawn, the nightrider, and the rook. Black would now be obliged to escape the check by recapturing the pawn with 2 Kxe6 or passively evading the check from the rook without capturing by playing one of either 2 Ke7, 2 Ke8, 2 Kg6, 2 Kg7, or 2 Kg8.

In xiangqi, the Chinese version of chess, triple check and even quadruple check are possible, as in the following examples. In janggi (Korean chess), even quintuple and sextuple check are possible as well. Triple check: Red moved his horse from e5 to d7, giving check and exposing a double check from the chariot and cannon. Quadruple check: Red moved his chariot from f9 to e9, uncovering two checks from the horses, giving a check of its own, and making a platform for the cannon at e7 to give yet another check. In janggi, using the same pieces and adding two elephants that both attack the general through the chariot's square allows a sextuple check.