The Philidor Position
In the poisiton above, Black's easiest Draw is to move Ra6. As the long as the King cannot reach the 6th rank in front (there is a parallel here with King and Pawn endgames, where if the pawn reaches the 6th rank ahead of the king, the result is usually a draw).
If the king does manage to reach the 6th rank ahead of the pawn, (say if Black plays Rf1+ by mistake), the Black king will have to evacuate the queening square. The reason is that the Kings are now in opposition, and White can either checkmate or force a winning king and pawn endgame. In these positions the King should always run to the short side of the board.
With the king safely on the short side (see diagram below), Black has two defensive strategies: checks from the side and checks from behind.
Checks from behind allow White to advance the pawn with 1. Kd7 Rd1+ 2. Ke7 Re1 3. e6. White would then shift the Rook to d8 and repeat the pattern to set up the Lucena position. If the Black king attacks with f6, then Rf8+ wins.
Black's better strategy is moving Ra1 to set up checks along the ranks. White must then shift the rook to d8 prematurely to block the checks. Then the Black rook simply goes back e1. White's advance pattern won't work because trading rooks leads to a won king and pawn endgame.
Checks from the side work best when the Black rook has three files between himself and the White king. If there are only two files the White king could win a tempo by attacking the Black king while avoiding the check. This would allow the pawn to advance.
So in short:
- forcing the pawn to the 6th rank in front of the king draws, just as it does in a king and pawn endgame.
- if the king does reach the 6th rank, the black king will have to run. Once the king runs, Black's best plan is to check along the files. If white threatens to block the checks, the black rook moves back behind the pawn.
- checks from behind also work when the white rook does not protect the pawn. Otherwise the pawn will be able to ratchet up the board.