This is the Lucena Position 1.Rg1+ Kh7 [1...Kf6 2.Kf8 wins] 2.Rg4 to build a bridge 2...Rd2 [2...Ra8+ 3.Kf7 wins] 3.Kf7 Rf2+ 4.Ke6 Re2+ 5.Kf6 Rf2+ 6.Ke5 Re2+ 7.Re4 and the bridge is complete and the pawn will queen *