An endgame study from 1951 by Vladimir Korolkov.
White to move and win.
Solution:
1.f7 Ra6+
1...Rf6? 2.Bb2
2.Ba3!
2.Kb2? Rf6
2...Rxa3+ 3.Kb2 Ra2+
3...Rb3+? 4.Ka2 followed by f8Q+.
4.Kc1!!
4.Kxa2? Be6+ and next Bxf7 with draw.
Also 4.Kc3? Rc2+ 5.Kb4 (5.Kxc2 Bxf5+ and next Kg7 winning the pawn; 5.Kd4?? Rd2+ followed by Rd8) 5...Rb2+ 6.Kc5 Rc2+ 7.Kb6 Rb2+ and black holds draw. If 8.Kc7 then 8...Rb7+ followed by Rxf7.
4...Ra1+
4...Rc2+? 5.Kd1
5.Kd2 Ra2+ 6.Ke3 Ra3+ 7.Kf4 Ra4+ 8.Kg5
Not 8.Ke5?? Ra5+ and next Rxf5.
8...Rg4+! 9.Kh6!
9.Kxg4? Bxf5+ 10.Kxf5 Kg7 11.Ke6 Kf8 12.Kf6 stalemate.
And on both 9.Kf6 and 9.Kh5 black has 9...Rg8! holding draw.
9...Rg8!
A better try than 9...Rg6+ 10.Kxg6 Bxf5+ 11.Kf6! followed by f8Q+.
10.Ne7! Be6
10...Rf8 11.Ng6 mate.
11.fxg8Q+! Bxg8 12.Ng6 mate.
