Black & White cooperate to reach a position in which the Black King is checkmated in the smallest amount of moves.
So Black actually is suicidal while White is sitting back...
"Never interrupt your opponent while he is making a mistake."
(I Googled that quote - Napoleon Bonaparte is supposed to have said it)
But this is not so much about black & white being big enemies; it is more like they are love partners. They collaborate in order to reach a climax. ;-)
Recently, a German Dude showed me the longest (orthodox) helpmate in terms of length composed to date; a H#28. There were some composers who made longer ones... but all of those were terribly cooked.
In the following position, the 28-move path to suicide is unique - neither side can deviate from these moves.
This effort by Bernhard Hegermann has not been surpassed ever since it was published back in 1934.
So I'll make a longer one and rewrite helpmate history. Watch this space :-P
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