View source for Double check

{{Short description|Chess term; a check delivered by two pieces simultaneously}}
{{other uses}}
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|From this position, 1.Bxe5++ is a winning double check.
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In [[chess]] and other related games, a '''double check''' is a [[check (chess)|check]] delivered by two pieces simultaneously.<ref name="HooperWhyldp.113">{{Citation|last=Hooper|first=David|author-link=David Vincent Hooper|last2=Whyld|first2=Kenneth|author-link2=Kenneth Whyld|title=[[The Oxford Companion to Chess]]|year=1992|edition=second|page=[https://archive.org/details/oxfordcompaniont0000hoop/page/113 113]|publisher=[[Oxford University Press]]|isbn=0-19-866164-9}}</ref><ref name="Golombekp.88">{{Citation |last=Golombek |first=Harry |author-link=Harry Golombek |title=Golombek's Encyclopedia of Chess |year=1977 |page=88 |publisher=Crown Publishing |isbn=0-517-53146-1 }}</ref> 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]].<ref>Tim Just and Daniel Burg, 2003, ''U.S. Chess Federation's Official Rules of Chess'', 5th ed., {{ISBN|0-8129-3559-4}}, p. 218</ref>) This article uses "++" for double check and "#" for checkmate.
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==Chess==
{{Chess diagram  
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| Gundersen vs. Faul, 1928
|rd|  |bd|qd|  |rd|  |  
|pd|pd|  |  |nd|  |  |  
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|  |bd|  |nd|  |  |ql|  
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|pl|pl|  |  |  |pl|pl|  
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| After 14...g7–g5, White mates with a double check by capturing the pawn ''en&nbsp;passant''.
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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&ndash;Faul, 1928, Black has just played 14...g7–g5. White replies 15.hxg6 {{chessAN|e.p.}}#. 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 problem]]s.
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===Game examples===
A double check is a part of the [[smothered mate]] pattern known as ''Philidor's legacy''.

{{Chess diagram  
| tright
|Réti vs. Tartakower, 1910
|rd|nd|bd|  |kd|bd|  |rd
|pd|pd|  |  |  |pd|pd|pd
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|pl|pl|pl|bl|  |pl|pl|pl
|  |  |kl|rl|  |bl|nl|rl
|Position after 8...Nxe4??
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[[Aron Nimzowitsch]] wrote, "Even the laziest king flees wildly in the face of a double check."<ref>{{Citation |surname=Nimzowitsch |given=Aron |author-link=Aron Nimzowitsch |title=[[My System]] |year=1947 |edition=second |page=130 |publisher=David McKay  |isbn=0-679-14025-5 }}</ref> Because the only possible response to a double check is a king move, the double check is often an important tactical motif.<ref name="HooperWhyldp.113"/> A famous example is [[Richard Réti|Réti]]–[[Savielly Tartakower|Tartakower]], Vienna 1910, which arose after: 
:'''1. e4 c6 2. d4 d5 3. Nc3 dxe4 4. Nxe4 Nf6 5. Qd3 e5{{chesspunc|?!}} 6. dxe5 Qa5+ 7. Bd2 Qxe5 8. 0-0-0{{chesspunc|!}} Nxe4{{chesspunc|??}}''' (diagram) '''9. Qd8+{{chesspunc|!!}}'''
 
Réti [[Queen sacrifice|sacrifices a queen]] in order to set up a double check, as well as an unstoppable checkmate in two moves.
:'''9... Kxd8 10. Bg5++''' 

White mates after 10...Ke8 11.Rd8{{chessAN|#}} or 10...Kc7 11.Bd8#.<ref>{{Citation |surname=Chernev |given=Irving |author-link=Irving Chernev |title=1000 Best Short Games of Chess |year=1955 |page=18 |publisher=Simon and Schuster }}</ref>
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{{Chess diagram  
| tright
|Anderssen vs. Dufresne, 1852
|  |rd|  |  |kd|  |rd|  
|pd|bd|pd|pd|nd|pd|  |pd
|  |bd|nd|  |  |pl|  |  
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|ql|  |  |  |  |  |  |  
|bl|  |pl|bl|  |qd|  |  
|pl|  |  |  |  |pl|pl|pl
|  |  |  |rl|rl|  |kl|  
|Position after 19...Qxf3{{chesspunc|?}}
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A double check was also seen in the celebrated [[Evergreen Game]], [[Adolf Anderssen|Anderssen]]–[[Jean Dufresne|Dufresne]], 1852.<ref name="Golombekp.88"/> 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#'''
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===Variants===
{| align="right" border="0" cellpadding="1" cellspacing="0"
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{{Chess diagram small
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|Winning position for White shown with a pawn, a bishop, a rook, two moas (shown as inverted knights) and a [[Grasshopper (chess piece)|grasshopper]] (shown as inverted queen). After Black moves his only pawn to d5, White taking it ''en passant'' with their own pawn results in quintuple check. 
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{{Chess diagram small
|tright
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|__|__|__|__|__|__|__|__
|__|__|__|__|pd|kd|__|__
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|__|__|__|Nl|__|__|__|__
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|__|__|__|__|__|rl|kl|__
|Winning position for White shown with a pawn, rook, and a [[nightrider (chess)|knight-rider]] (shown as inverted knight). After Black moves his only pawn to e5, White taking it ''en passant'' with their own pawn results in triple check.
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|}

In chess with [[chess variant|variant rules]] or [[fairy chess piece|fairy pieces]], other ways of delivering a double check may be possible. The moves of ordinary chess pieces only permit a maximum of two pieces giving check at once, but in some variants, triple checks and higher may be possible.

For example, in the winning position shown to the left, after Black plays 1...d5 to remove the check from the bishop on c4, White plays 2.exd6 e.p.+++++. After the ''en passant'' capture, five pieces discover-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 multi-check and play one of either 2...Kxd6, to recapture White's pawn right away, or passively evade the checks without capturing by playing 2...Kd7 or 2...Kf6.

Another example is shown with the winning position shown on the right, after Black plays 1...e5 to remove the check from the knight-rider on d3, White plays 2. fxe6 e.p.+++. After the ''en passant'' capture, three pieces discover-check the black king: the pawn, the knight-rider, and the rook. Black would now be obliged to escape the multi-check by recapturing White's pawn with 2...Kxe6 or passively evading the checks without capturing by playing one of either 2...Ke7, 2...Ke8, 2...Kg6, 2...Kg7, or 2...Kg8.

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==Xiangqi==
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.
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|25}} ''Triple check:'' Red moved his horse from e5 to d7, giving check and exposing a double check from the chariot and cannon.
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|25}} ''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.
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==References==
{{reflist}}

{{chess}}

[[Category:Chess terminology]]

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