When the rulebook says “When the opponent can show a forced mate”, how soon does this mate have to be?
Example: Basic Chess Endings by Reuben Fine, Revised by Pal Benko, Pg 96, No. 191…here, if black runs out of time, for example, they couldn’t get a draw, right? Even though white only has a knight, the position of black’s pawns and king allow the white knight to mate. My question is, how far into the future is the “forced mate” required to be in? (Grandmasters can plan a forced mate sometimes in 15-20 moves or more)
I assume you are referring to 14E, Insuffcient material to win on time. There is no restriction on the number of moves. However, this is explicitly limited to K+B, K+N, and K+2N (no opposing pawns). Except possibly in composed studies, a multi-move forced mate is simply not going to occur. The point of this rule is to prevent a player from winning on time when he could not win over the board except by a helpmate.
Strictly speaking, it’s a form of composed problem where Black helps White to mate is a specific number of moves.
In the case we’re discusing, the simplest example is King and two Knights versus King. You can drive the King to the edge of the board and check him around, but the King will always have two squares. The only way it is possible to checkmate is for the defender voluntarily to move to the wrong one. You can’t give mate without help from the opponent, so you don’t have mating material, so you can’t win on time.
I played with the pieces for a while, and found that, if you don’t care about plausibility, it’s not hard to set up a “forced mate” in five or six with K+B vs. King and a lot of pieces. But, I reiterate, there isn’t one chance in seven hells of this ever coming up in a real game.