ReformedCharacter wrote:does 'forced' mean that each white move must put black into check\checkmate? I think I can see mate in 4 but 1 move does not give check.
Although a check is an obvious way of "forcing" (or at least restricting the choices for) your opponent's move, in puzzles that is usually not the case. Puzzles are something of an artform where the "key" to the solution is often a very quiet and unobvious move, perhaps involving a sacrifice to open up a line or close off an escape route for the King. Contrast this with the beginner habit of always checking if you can, which is rather crude and often ineffective. ("Never miss a check, it might be mate" is an old chess joke).
Puzzles are about elegance and efficiency. Note also that good chess players are not always good chess puzzle solvers, and vice versa.
Gengulphus wrote:The normal meaning of a move being 'forced' is that there is only one legal move for the player of the move. For example, if it were black's move in the position in the diagram rather than white's, the only move black could make would be to advance the g4 pawn to g3, since all the other black pawns are blocked and all unblocked black king moves would be moves into check, so black's move would be 'forced'.
Yes, although I think there is another sense of the word "forced" which means that, whilst there is a choice of more than one legal move, only one doesn't lose immediately.
So some puzzles might say "white to play and win in four" but if black plays a move other than the best move, he loses in less than four. So that best move is "forced" if you want to survive as long as possible.