To use a simple example, tablebases show that KQ vs. K is won in at most ten moves. But chess books going back many decades, well before tablebases, say the same thing. How was this calculated?
2 Answers
Nothing was calculated. They arrived at their results by trial and error.
Some guy would start with a seemingly disadvantageous position and tried to find the shortest mate. His result remained valid until the next guy found a more disadvantageous position or a quicker mate.
A long time later, engines became powerful enough to calculate simple endgames like K+Q v K simply by exhausting all possibilities, but by that time technology was also advanced enough to create the first tablebases.
Well, it is calculated by tablebases. I can't imagine anybody declaring a definitive number for the minimum moves needed to achieve checkmate with KQ vs. K.
answered Jan 27, 2017 at 20:49
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1Well, then you should look into some old books ... ;-) Commented Jan 28, 2017 at 8:30
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2To be fair, there is a big difference between KQ-K and KQ-KBB. But yes, those books. Commented Jan 28, 2017 at 10:29
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And how useful are those numbers? If you can mate with KQ vs K in about ten moves, you know you understand it. Likewise if you can consistently do KBN vs K in less than 50. There is nothing comparable for KQ vs KBB. The useful information was on the whole produced mostly by human beings. Admittedly, KQ vs KR is a marginal case. And, yes, I do know about John Nunn's work. Commented Jun 9, 2017 at 16:15