Let us return to the case where the black king is in front of the pawn but Philidor's position cannot be reached.
Here black cannot play Rb6 because white already owns the sixth rank. But black has another way to draw.
1...Rf1
Black is following a policy of attacking the pawn from the rear while trying to keep the king in front of the pawn. At the same time, black will stay alert to the possibility of checking the white king from the side or the rear. What can white do in this position? 2.f6 allows black to start never ending checks from the rear because white can no longer hide his king in front of the pawn. 2.Ra8+ or 2.Ra7 don't accomplish anything nor does Rf6+. (2.Rf6+ Kg7 There is no way for white to progress except to start over again.) All that is left is 2.Kg6 and 2.Kf6.
2.Kg6 doesn't accomplish much. 2...Rf2 3.Ra8+ Ke7 White cannot advance his pawn nor his king. 4.Ra7+ Kf8 Black returns to his policy of attack the pawn from the rear and keep the king in front of the pawn. Black can only improve by moving his king to f6. He might as well have done that at move 2.
So instead of 2.Kg6 white will play 2.Kf6 Now black must move his king to avoid mate. After 2.Kg8 or 2.Ke8 his king will be safely situated a knight's jump from the enemy king. Which move should black choose. Keeping in mind that black wishes to stay alert to the possibility of checking white's king from the side, we realize that black's rook will want to check from a file as far from the white king as possible to reduce white's ability to counterattack the rook with the king. So the rook will go to the b file (the long side of the board. In order to avoid the possibility of the black king getting in the way of the black rook's checks, we should decide to move the black king to the short side of the board.
2...Kg8
Our new policy is:
2. keep the king in front of the pawn
3. if that is not possible, place the king on the short side of the board a knight's jump from the enemy king.
3.Ra8+ Kh7
We have reached the position of the next diagram.
If white could get his rook to the g file cutting off the black king, he could reach the Lucena position. But this is impossible. Rg8 loses the rook and moving the rook off the 8th rank allows black to return his king to g8. White has three possible plans:
1)Move his king out of the way of his pawn
4.Ke6 Kg7 The pawn cannot advance 5.Ra7+ Kf8 and black has his king back in front of the pawn again.
2)Support the advance of his pawn with the rook
4.Rf8 Ra1 Black is ready to check from the long side 5.Ke7 .Ra7+ 6.Ke6 Ra6+ 7.Kd7 Ra7+ 8.Kc6 Ra6+ 9.Kb5 Rd6 The white king is cutoff from the pawn. White no longer has any chance to win 10.Kc5 Rd1 11.f6 Kg6 12.f7 Kg7
3) A better plan is to try and block black's checks
4.Rf8 Ra1 5.Re8 white positions his rook to where it can block the checks so black returns to attacking the pawn 5...Rf1 6.Re5 Kg8 7.Kg6 Kf8 8.Kf6 Kg8 9.Ke7 Kg7 The black king and rook prevent the pawn from advancing).
3.2 An important draw
The next diagram is similar to the previous diagram but the rook is not behind the pawn. It is still a draw.
If 1 .Rf8 Ra1 we are back to a position discussed for the previous diagram under heading 2.
If instead 1.Kf7 Rb2 2.f6 we have the following diagram
Same as the previous diagram only white has managed to advance his king and pawn one rank. It doesn't do him any good. It is a draw.... Rb7+ 3.Ke8 [3.Ke6 Rb6+ 4.Ke7 Rb7+ 5.Ke8 Kg6] 4...Kg6 ,draw .
Pawn on the 6th rank or 5th rank, it is still a draw . The last two diagrams show the key drawing position that we will aim for in the f&h pawn ending. After capturing the h pawn we want to get our king to h7 with our rook in the far corner or directly behind the pawn.