Euwe-Aljechin Amsterdam 1935 problem I came across this puzzle that I couldn't solve and after looking at the solution I am still not sure what is going on here.


[FEN "5k2/p5pp/r7/2pB2p1/b1P5/6P1/4PP1P/R5K1 w - - 0 1"]


The best move apparently is Ra2. 

The problem says "white to play and win". The situation after Ra2 seems quite balanced to me and Stockfish is not detecting a clear advantage for white. 

Any views on this?
After 1.Ra2, black's rook and bishop are both stuck; 1...Bb5, defending the rook on a6 while attacking the rook on a2 is no longer effective since 2.cxb5 defends the rook on a2. After this, black's play is completely shut down due to the pin on the bishop, while white is able to make improvements in his position. In particular, white can get a very strong passed pawn on the e-file which black can do nothing about.

This is why the position is so-called strategically winning for white after 1.Ra2. Unlike other types of winning advantages, this one is of quite a long-term nature, and white would still need to show good general understanding and endgame technique to win the game in the end. Let's look at a couple of sample lines:

 [FEN "5k2/p5pp/r7/2pB2p1/b1P5/6P1/4PP1P/R5K1 w - - 0 1"]


 1.Ra2! (1.Ra3? Bb5! {and black escapes the pin in an elegant manner; the bishop on b5 is temporarily immune due to the hanging rook on a3.}) {Paralyzing black's bishop and rook.} 1...g4 {Might as well try to stop white's pawns from advancing.} (1...Bb5?? {This is a terrible blunder now.} 2.cxb5 Rxa2 3.Bxa2 {and white is just a piece up.}) 2.e4 {Push the pawn! A strong and far-advanced passed pawn makes black's movements even more awkward than before.} 2...g5!? {Other defensive tries are available as well, but black wants to keep white down, and doesn't want to allow white's king access into black's position via f4.} 3.e5 h6 4.h4! {Black is given the chance to pick his poison} 4...Kg7 {The most resilient path.} (4...gxh4 5.gxh4 {and white's king is given access to black's camp via f4.} 5...Kg7 6.Kh2 Kf8 7.Kg3 h5 8.Kf4 Kg7 {What now? How does white proceed?} 9.Ke3! {White uses triangulation to put black on the move, thus gaining ground} 9...Kf8 10.Ke4 Kg7 11.Kf4 Kg6 {Black needs to stop white's king, but this allows a tactical trick:}   (11...Kf8 12.e6 Ke7 13.Kg5 {and black is getting squeezed to death.}) 12.Bb7! Rb6 13.Be4+ {and white wins the bishop on a4.}) (4...gxh3  5.f4! {and white creates two strong connected passed pawns. These are unstoppable, and will decide the game.}) 5.Kf1 Kf8 6.Ke1 Kg7 7.Kd2 Kf8 8.Ke3 Kg7 9.h5 {Finishing preparations before liquidation into a winning rook ending by placing king and pawns optimally.} 9...Kf8 10.Bb7! {The way to make progress!} 10...Rb6 11.Rxa4 Rxb7 12.Ra6 {Black's position is starting to crumble, and there is no way to defend all weak points anymore.}


So in conclusion, yes white is winning after 1.Ra2! but the win isn't trivial, and precision is still required afterwards to win the game.