Section A1 – Win
1.Bg2!
(1.Kf7? Rh3! 2.Bb7 Rh7+ 3.Kf6 Rh6+ 4.Kxf5 Rh5+ 5.Ke4 Rg8 6.a8Q Rxa8 7.Bxa8 Ra5 8.Bb7
Kxe6=.)
1…Rxg2 2.Kf7 Rg8!
Counter-sacrifice.
3.Kxg8 Kxe6 4.a8R!
(4.a8Q? Rd8+ 5.Qxd8= Stalemate.)
4…Rd7! 5.Rb8!
(5.Re8+? Kf6 6.Rb8 Kg6! 7.Rb6+ Kh5=; 5.Rc8? Kd5!=.)
5…Ra7
(5…Kd5 6.Rb7+-.)
6.Rb5!!
Suddenly sacrificing a passing pawn. 6.Rb6+? Kd5=.
6…Rxa6 7.Kg7 Ra7+
(7…Ra1 8.Re5+ Kd6 9.Kf6+-.)
8.Kg6 Ke7 9.Rxf5 Ke8
(Or 9…Ra1 10.Rf7+ Ke8 11.f5 Rf1 12.Kg7! Rg1+ 13.Kf6+-.)
10.Rf6! Ra1 11.Kg7 Rg1+
(11…Ra7+ 12.Kg8+-.)
12.Rg6 Rf1 13.Re6+
1-0.
An instructive rook endgame after underpromotion.