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coolmtclmr 31-Jan-11, 03:33 |
 perpetual check |
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Declare... There are 'perpetual check' situations that can arise in which checks can not be escaped, and which apparently will go on forever. Actually they won't, of course. Eventually some position or other will be repeated 3 times. Only then can a declaration be upheld. Note that the repetitions can occur at any time, and need not take place in quick succession. Here's an example A diagram similar to this I posted recently in another thread, but in an entirely different context. w With 1.Rh7ch White inaugurates a series of checks with the rook that were Black to take, the result would be instant Stalemate. So the BK runs: 1.Rh7ch Kg7 2.Rg7ch Rf8 ... etc You can see that this could go on for ever. Suppose, then, Black were bloody-minded enough to run all the way to a8 and back to h8 etc. Then on move 2, 14 and 16 the same position will have occurred, whereat a draw can be claimed (declared). In some situations, perhaps the checks could go on for 50 moves, but the <Declare> button allows a claim for that reason as well. Reverting to the three-fold repetiton, note that the position repeated has to be identical in every respect: whose move it is, and whether castling or 'en passant' captures are available. However, it does not matter which rook or knight is standing upon a particular square, though it isn't easy to imagine a repetition in which one's rooks or knights have swapped places! Note, too, that it is repetition of POSITION that's at stake, not repetition of MOVES. Note that in the above example, the position repeated is arrived at by a different move on move 14 than that of moves 2 and 16. Cheers, |
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"Note that it is repetition of POSITION that's at stake, not repetition of MOVES." "Note that the position repeated has to be identical in every respect: whose move it is, and whether castling or 'en passant' captures are available. However, it does not matter which rook or knight is standing upon a particular square, though it isn't easy to imagine a repetition in which one's rooks or knights have swapped places! Note, too, that it is repetition of POSITION that's at stake, not repetition of MOVES. interesting points, ion, will remember them, Thank you. |
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