Monday, April 5, 2010

The concept of checkmate

Next time you have the difficult task of explaining checkmate to a beginner at chess, maybe the ideas in this post will help.

Newcomers often feel that it is somehow unsatisfactory that they never actually capture the king itself. Indeed (according to Wikipedia) "In early Sanskrit chess (ca. 500-700) the king COULD be captured and this ended the game ... Later the Persians added the additional rule that a king could not be moved into check or left in check. As a result, the king could not be captured. Checkmate was thus the logical and only decisive way of ending a game (since if it was checkmate, any move would be illegal)".

That's the usual concept - but, if they don't accept this argument (and it's certainly a bit purist for, say, the youngsters) maybe you have to talk around the issue a little. Try this for size!

"You can think of checkmate as representing the inevitability of loss of the king. If the game did continue until the king was captured, then you could give check from a checkmate position, but you'd still lose. The opponent wouldn't be forced to move his king; he'd take yours. I think that's the clearest way of explaining why the checkmate rules are the way they are." (being an unattributed reply to one Bubba73 in one of the Wiki edit pages)

Of course there's always someone who asks the awkward questions (!), thus:

Q. Can you - while your king is in checkmate - move your piece to put your opponent's king in check, ultimately forcing your opponent to move his king, and avoiding your own checkmate?

A. No. If your king is in checkmate, the game is over and you lose. If your king is in check but not in checkmate, you can check the opponent's king - if that move gets you out of check. (Bubba73)

There's more in a similar vein at the end of this post - but this last comment intrigued me ie the idea of avoiding checkmate by moving a piece which puts the opponent's king in check ... or even checkmate!

And so, dear reader, I present a game in which this actually happened in match play (of course I would be delighted if you can post other examples in the comments). I originally found this game in a Yahoo ANSWERS page.

OK, so now you are armed with lots of material to explain the concept of checkmate fully and completely. Or are you? Is your mythical newcomer still unconvinced with your explanations? Here, in a discussion on a Wiki editing page, is there more to be said?

What's the reason for all the rules about checkmate and check when the goal is so obvious?

What I'd really like to be explained in this article is why chess stops one move before the real goal (capturing the king) is achieved. To my knowledge, this makes chess different from all other board games. For example, playing Checkers you haven't won by saying "whatever you do, the next move I'll capture all your remaining pieces". You actually have to capture them, just saying that you can in the next move is not enough (you don't have to prove it either). Furthermore this seems to make the rules of the game unnecessary difficult. If the game would simply end by capturing the king, it's pretty obvious that a check-situation is not very desirable and you'd want to do something about that instead of moving around some other pieces. You wouldn't need the rules to include the word "check". I guess it's got something to do with politeness, it's not nice to have your king actually captured so there's no need to keep on fighting until the inevitable outcome comes true, but I'd say that the politeness should be shown by the loser instead of the winner (as the article points out, the loser should resign when he knows he is to lose, so if he didn't see it coming, why not simply resign in the very last move?). From a programmer's point of view: a program that values the optimal situation to be when the opponent's king is captured is a simpler than a program that would try to reach a checkmate situation (which would have to do exactly the same calculations). I guess a professional chess player thinks in a similar vein, not trying to reach checkmate but trying to kill the opponent's king. Joepnl 3 March 2010

I don't think it makes the rules unnecessarily difficult. In chess the king is never captured. In ancient times they probably considered it undignified for the king to be captured or didn't want games to be decided simply because poor play allowed the king to be captured. They wanted capture to be inevitable. You can't put it in check and you can't leave it in check. It is different from checkers. As far as programs - I think they do play that way. They give the king a higher value than all of the other pieces combined, and then the program will do anything to achieve or avoid checkmate. That should also be easier than programming in checkmate, and should execute faster too. Bubba73 3 March 2010

Thank you for your contributions to the article. I didn't know (but did expect) ancient rules did say that in order to win you have to capture the king. It's very interesting that first check was invented and checkmate later. I thought the humiliating capture of the king was the origin of checkmate, check logically following that rule, but it's the other way around. I still find it kind of curious that chess is the only (to my knowledge) board game (of for that matter, any game) that has a build-in protection against losing for making mistakes, but I guess life would get really boring if all mysteries were dissolved instantly on Wikipedia :) Joepnl 4 March 2010

Thank you. As far as I know that is only true about chess. The king in chess came from the king, the monarch, and that must be why it is special - opposed, say, to kings in checkers/draughts. But also losing the king ends the game - accidentally losing other pieces doesn't (checkers and chess). Bubba73 4 March 2010

STOP PRESS: I have found this issue neatly and interestingly discussed (page 48) in Paul Hoffman's "King's Gambit" - which I am thoroughly enjoying.

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