Opposition and Outflanking

Knowing how to gain and keep the opposition is essential in pawn endgames. But, the opposition is not an end in and of itself. Opposition is useful only when it leads to an outflanking maneuver. Sometimes the outflanking comes first, leads to gaining the opposition, and then culminates in a decisive outflanking. Such was the case in this seemingly simple pawn endgame from Dvoretsky's Endgame Manual. Dvoretsky attributes the position to J. Drtina, 1907. I played the position against Rybka 4, which went for a line given in Dvoretsky's notes. In Dvoretsky's main line, the play is all on the kingside. In my battle with Rybka, the whole board came into play. Note that I first gain the opposition from a distance of two files away.