This article uses algebraic notation to describe chess moves.

From this position, 1.Be6++ is a typical double check.

A position demonstrating how double check without the moved piece giving check is possible. Black's last move was 1...g5 (from g7).

In chess, a double check is a check delivered by two pieces at the same time.^[1][2] In chess notation, it is often symbolized by "++".

The most common form of one check involves one piece moving to deliver check, at the same time revealing a discovered check from a piece behind (such a check is an inherent part of the type of smothered mate known as Philidor's legacy). The only replies to a double check are king moves, as capturing the checking piece (except by the king, which in the process moves out of check by the other piece) is not an option since there are two of them, and interposition is likewise impossible as there would be two lines of attack to block.

In exceptional circumstances, it is possible for the piece moved not to give check. The only way for this to happen in orthodox chess is by way of an en passant pawn capture. In the position shown above right, Black has just played 1...g5 (from g7). White replies 2.hxg6 e.p.++. This is a double check even though the pawn that White just moved is not giving check. Rather, one check is given by the rook, the other by the bishop; the former is discovered by the movement of the capturing pawn, the latter by the removal of the captured pawn. Such a double check is extremely rare in practical play, but is sometimes found in problems.

Réti-Tartakower, position after 8...Nxe4??

Anderssen-Dufresne, position after 19. ... Qxf3?

Aron Nimzowitsch wrote that, "Even the laziest king flees wildly in the face of a double check."^[3] Because the only possible response to a double check is a king move, the double check is often an important tactical motif.^[1] A famous example is Réti-Tartakower, Vienna 1910, which arose after 1.e4 c6 2.d4 d5 3.Nc3 dxe4 4.Nxe4 Nf6 5.Qd3 e5?! 6.dxe5 Qa5+ 7.Bd2 Qxe5 8.0-0-0! Nxe4?? 9.Qd8+!! (sacrificing a queen in order to set up a double check) Kxd8 10.Bg5++ and White mates after 10...Ke8 11.Rd8# or 10...Kc7 11.Bd8#.^[4] A double check was also seen in the celebrated Evergreen Game, Anderssen-Dufresne, 1852.^[2] From the diagram at right, Anderssen won with 20.Rxe7+! Nxe7 21.Qxd7+!! (a queen sacrifice to set up a deadly double check) Kxd7 22.Bf5++ Ke8 (or 22...Kc6 23.Bd7#) 23.Bd7+ Kf8 24.Bxe7#.

[edit] Variants and triple check

With moas (white dots), moving the bishop results in triple check.

In chess with variant rules or fairy pieces, other ways of delivering a double check may be possible. Triple checks may also be possible, for example in the position shown, White plays 1.Ba8 triple check (the moa is a non-leaping knight which first takes a diagonal step, then an orthogonal one). After the bishop moves, both moas and the queen check the black king.

In Xiangqi, a Chinese version of chess, triple check is possible even without using fairy chess pieces. An example is as follows:

10 9 8 7 6 5 4 3 2 1 a b c d e f g h i Triple check: Red moves his horse from e5 to d7, giving check and exposing a double check from chariot and cannon.

[edit] References