Originally posted by Acolyte
The usual definition of a forced mate is one in which no matter what one player does, the other can ensure checkmate by optimal play.
But can you think of a position in which no matter what the players do, checkmate within a certain number of moves is completely unavoidable? A more difficult challenge is to think of a position with such a forced mate, bu ...[text shortened]... e may take several moves to occur. How many moves away from the inevitable mate can you manage?
OK this is my best effort.
White has 2 black bishops as he has "queened" one of his pawns into a bishop (bishoped?) I think the position is legal.
With white to move, it's inevtiable that he can only move his pawn, which will reach the 8th rank in 6 moves, before the black king can take it. No other pieces can move.
Of course, this only works providing white doesn't turn his pawn into another bishop or a knight!!!