1.Rf4
White takes possession of the 4th rank straight off [ White can not win by simply moving his king out and zig-zagging down the board towards the rook... 1.Ke7
Re2+
2.Kd6
Rd2+
3.Kc6
Rc2+
4.Kb5
Rb2+
5.Kc4
Rd2
and Black wins the pawn.; White actually has a second winning method available: 1.Ra1
with the idea of evicting Black's rook from the c-file, thus providing another route for the king to emerge without those bothersome checks. After the rook takes his place on c8, it will be protected by the pawn and in position to eventually protect the new queen on d8, effectively preventing Black from either exchanging rooks or defending the queening square. 1...Kf7
2.Ra8
Rc1
( If 2...Ke6
3.Ke8
Rh2
threatening mate on h8. 4.Ra6+
Kf5
5.d8Q
) 3.Rc8
the first step in the process; the Black rook must leave the c-file. 3...Rd1
4.Kc7
Rc1+
5.Kb6
Rb1+
6.Kc5
the second part: White will zig-zag down the board until Black runs out of checks, then queen his pawn.]
1...Rc1
2.Ke7
Re1+
3.Kd6
Rd1+
4.Ke6
[ 4.Kc6
also works.]
4...Re1+
[ If 4...Rd2
then 5.Rf5
intending 6.Rd5, again shutting out the Black rook.]
5.Kd5
Rd1+
6.Rd4
and once again the pawn will queen. *