Puzzle of the week #17

Chess Diagram: 

[Event "Puzzle #17"][Date "2008.04.24"][Result "?-?"][SetUp "1"][FEN "8/8/8/6pp/4rp1k/7P/5RPK/8 b - - 0 56"]56...g4

This weeks puzzle comes from a recently (last month) played game in the Dutch Championship. Both players were Grand Masters and played a long, hard fought game up to this point (see diagram). Black is up a pawn and pressing really hard. Questions:
1. What is the result of this game if Black moves 56... g4? Write a variation as long as needed to support your response (4 points)
2. What rule applies this time? (1 point)

Total available points for this puzzle is 5 (4+1). The answers will be published next week together with puzzle #18.

Puzzle #16 solution:
In a Kings and pawns endgame the most important thing to notice is the existence of passed pawns! The reason for it is passed pawns keep the opposite King tied up to stop them from advancing. Here White has a passed pawn on the 6th rank which is also defended; that means the White King can move freely. The rule applying to passed pawns is the square rule, marking the area of the board where the King can move and still stop the pawn. Kg4 can move all the way to c6-d6 and still be able to catch "h6" if it starts moving. Kf8 cannot move farther than e8-e7. The winning plan is now simple to put together: move Kg4 all the way to e6 and catch Black in zugzwang (any move loses). Here is the correct line:

[Event "Puzzle #16"][Date "2008.04.17"][Result "1-0"][SetUp "1"][FEN "5k2/8/5pPp/5P2/6K1/8/8/8 w - - 0 1"]1.Kf4 Ke8 2.Ke4 {White has the distant opposition} 2...Ke7 3.Kd5 Kf8 {The black King is tied up to the g6-passer} 4.Kd6 Kg8 5.Ke7! h5 (5...Kg7 6.Ke6 {Black is in zugzwang. It either loses the f6-pawn or the h-pawn if it starts moving}) 6.Kxf6 h4 7.g7 h3 8.Kg6 h2 9.f6 h1=Q 10.f7#

Correct solutions:
John D, Jacob, Katerina and Jeremy - 6 points
Jakab - 5 points
Karl - 3.5 points
Matthew and Wilson - 2.5 point
Joanne, Algerd and Alejandro - 1 point

46.0 John D
43.0 Jeremy
40.0 Jacob
33.0 Matthew
23.5 Katerina and Karl
17.5 Joanne
15.5 Frank
11.0 Bryant and Wilson
13 more solvers with less points