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Escaping a double check

The answer to Is it possible to block a double check? says

Moving the king is the only way to escape a double check. There is no possible other move that will block both checks.

But in the following situation, is it allowed for Black to escape by taking the Rook (placing White in check) and forcing a sacrifice of the Queen? If not, why not?

Black to move. Never mind how it got to this position, it's for illustration.

enter image description here

Rewan Demontay
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Weather Vane
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    "Never mind how it got to this position, it's for illustration" -- a bit too glib. You position doesn't work, but if it did it would be irrelevant since there is no legal way that it could arise. – John Coleman Mar 05 '22 at 12:56
  • @JohnColeman I am interested in getting out of such a position, not unhelpful comments restating what I already put. – Weather Vane Mar 05 '22 at 13:03
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    The point of my comment is that when trying to understand the rules of chess, it isn't helpful to wonder how they apply to positions which can never arise. When crafting a position, why not do the extra work to make sure that it can arise via a legal sequence of moves? – John Coleman Mar 05 '22 at 13:06
  • @JohnColeman a double-check *can arise*. I apologise for offending your sensibilities. I could have made a better example, but isn't recommended to change a question after answers have been posted which would invalidate them. I'll heed your advice next time. – Weather Vane Mar 05 '22 at 13:17
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    Is the starting position legal? Looks like it requires an illegal move to reach. From the first position, Black is **checkmated** and does not get a move. – SecretAgentMan Mar 05 '22 at 14:38
  • @SecretAgentMan thanks for your valuable input, please read the preceding comments, which cover it nicely. – Weather Vane Mar 05 '22 at 15:17
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    For future visitors, this question could be greatly improved by using a valid position. The OP's current 3 position sequence is illegal. – SecretAgentMan Mar 05 '22 at 17:32
  • Here's a legal double check position which I think represents the situation you want to cover, sidestepping this issue: https://lichess.org/editor/1k4q1/pp6/N7/8/8/6B1/8/6K1_b_-_-_0_1 – llama Mar 05 '22 at 23:43
  • @llama thanks but it isn't quite, because the Queen can't be taken after taking the bishop. I thought the question was simple enough but I'll give some more explanation. It's not *supposed* to be a real game. It's about a coding challenge, where the given position might be anything, the incorrect number of pieces, or an invalid position (possible responses) but the moves are standard. That's what I am solving, and I wanted to make sure this really is an inescapable checkmate. I didn't expect to be murdered, or have revenge downvoting elsewhere. – Weather Vane Mar 06 '22 at 00:26
  • "*I didn't expect to be murdered*" seems needlessly hyperbolic. If downvoting elsewhere is happening because of your question, that is not right. Your question is fine to me. The original question contained no context about "coding" and naturally caused some confusing regarding legal moves. – SecretAgentMan Mar 06 '22 at 00:55
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    An important thing to remember when thinking about chess situations: if you capture the opposing king, you win. – Mark Mar 06 '22 at 05:15

3 Answers3

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Not allowed, no.

White gives two checks (hence double), and meeting one isn't enough. After blacks reply Qxe8+, blacks king is still in check which makes Qxe8+ an illegal move.

Black is thus checkmated in your position.

starrin
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  • A similar question on [Quora](https://www.quora.com/Suppose-in-chess-my-king-got-checked-but-at-the-same-time-I-have-the-opportunity-to-check-my-opponents-king-Now-both-of-our-kings-are-checked-Would-the-game-end-in-a-draw-or-would-this-be-illegal) (I don't have an account) says *"... It may be possible to play a move that blocks the attack on your King while giving check to the opponent's King, but it is very seldom you'll have the opportunity to do that..."* – Weather Vane Mar 05 '22 at 11:16
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    @WeatherVane that's possible in single check situations but not double checks. If your king is being attacked by another piece after you make your move, that's an illegal move. – llama Mar 05 '22 at 23:48
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    @WeatherVane: If it helps, you can think of it as "whoever captures the enemy king first wins" (we just end the game before that actually happens). In your second image above, it's white's turn so he can play Nxa8 before black can play Qxe1. – BlueRaja - Danny Pflughoeft Mar 06 '22 at 00:20
  • Is there a move (in other double checks, not the above one) that blocks *both* checks, *and* puts the opponent in check? That would be very "call an ambulance... but not for me". – stevec Mar 06 '22 at 02:15
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    @stevec that could be another question, but it's not possible to *block* a double check because if the checks are blockable, they have to be along different directions (pick two of rank, file, diagonal) so one square can't block both. It's pretty easy to construct something where you move out of double check and put the opponent in check though: Rd4+ for white here would be bad for that reason https://lichess.org/analysis/8/8/1r1k3K/8/5R2/6B1/8/8_w_-_-_0_1#0 – llama Mar 06 '22 at 03:04
  • @llama nice, I thought that might be the case, but in chess, I never rule anything out without checking, as there is often some crazy exception that proves the initial hypothesis incorrect. Thanks for confirming. – stevec Mar 06 '22 at 03:07
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For this kind of questions, if you have doubts, just play chess with the goal of capturing the enemy king. The first player to capture the enemy king wins. This isn't the official rule, but it's effectively the same in almost all situations I'm aware of (it doesn't work for stalemate).

So after 1...Qxe8+, White wins with 2. Nxa8. It doesn't matter that Black also threatens to capture White's king with 2...Qxe1, since White has already won.

Allure
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A legal way to get into the same kind of situation:

enter image description here enter image description here

But as others have posted: It is illegal to make a move that places or leaves one's king in check.

Velvel
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