user12554: 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?

user70: My Stockfish disagrees with your Stockfish. It's still grinding but the jig is up. The issue is that Black's Bishop and Rook are pinned down and defensive and White has a passed e-pawn that can be supported on the 6th rank.
Also, Black is nearly in Zugzwang.


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

1.Ra2 g4 (1... Bb5? 2. cxb5 Rxa2 3. Bxa2) 2.h3 h5 3.e4 Ke7 4.e5 Kf8 5.hxg4 hxg4 6.Kf1 Ke7 7.Ke1 g6 8.Kd2 g5 9.Ke3 Kf8 10.Kd3 Kg7 11.Bb7 Rb6 12.Bc8 Rb4 13.Ke4 Rxc4+ 14.Kf5 a6


Yeah, these moves are very robotic. Black's g4 is about as good as it gets. Ke7 and h5 are much worse for Black than g4.
So, why Ra2? After 1 ... Bb5, white has 2. bxb5 and the White's bishop defends the rook. So sneaky.
EDIT - I let the computer play the game out, 5 minutes per move. It would not be easy to win this.  What I am seeing is that the initial analysis is generally good, but Stockfish gains a lot of clarity by playing it out. We see that White's second move differs from the analysis above.


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

1.Ra2 g4 2.f3 gxf3 3.exf3 Ke7 4.h4 h6 5.Kf2 Kd6 6.Ke3 Ke5 7.f4+ Kf5 8.Kf2 g5 9.fxg5 hxg5 10.Bb7 Rb6 (10... Ra5? 11.Bc8+ Kf6 12.hxg5+ Kxg5 13.Bd7 Ra6 14.Rxa4 {and now black pays the price for allowing the pin}) 11.Bc8+ Ke4 12.Rxa4 Rb2+ 13.Kg1 gxh4 14.gxh4 Rb8 15.Be6 Rh8 16.Bd5+ Kd3 17.Kf2 Rxh4 18.Rxa7 Kd4 19.Kg3 Rh8 20.Kf4 Rh6 21.Rd7 Rh4+ 22.Kg5 Rh2 23.Bf7+ Ke4 24.Rd5 Rh8 25.Be6 Ra8 26.Rxc5 Rf8 27.Rd5 Ra8 {And now Stockfish announces a mate in 20+ moves, or something, lol}



user14672: In the problem position, the black player is set to liberate his rook by playing his bishop to b5 as mentioned above. Significantly, the move of the rook to a2 is the only move that forestalls black's opportunity. The tactical resource involves the linking of the white bishop and rook and is an example of coordination of pieces.

user8300: 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.

12554: <p>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.</p>

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

<p>The best move apparently is Ra2. </p>

<p>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. </p>

<p>Any views on this?</p>
 70: <p>My Stockfish disagrees with your Stockfish. It's still grinding but the jig is up. The issue is that Black's Bishop and Rook are pinned down and defensive and White has a passed e-pawn that can be supported on the 6th rank.</p>

<p>Also, Black is nearly in Zugzwang.</p>

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

1.Ra2 g4 (1... Bb5? 2. cxb5 Rxa2 3. Bxa2) 2.h3 h5 3.e4 Ke7 4.e5 Kf8 5.hxg4 hxg4 6.Kf1 Ke7 7.Ke1 g6 8.Kd2 g5 9.Ke3 Kf8 10.Kd3 Kg7 11.Bb7 Rb6 12.Bc8 Rb4 13.Ke4 Rxc4+ 14.Kf5 a6
</code>
</pre>

<p>Yeah, these moves are very robotic. Black's g4 is about as good as it gets. Ke7 and h5 are much worse for Black than g4.</p>

<p>So, why Ra2? After 1 ... Bb5, white has 2. bxb5 and the White's bishop defends the rook. So sneaky.</p>

<p>EDIT - I let the computer play the game out, 5 minutes per move. It would not be easy to win this.  What I am seeing is that the initial analysis is generally good, but Stockfish gains a lot of clarity by playing it out. We see that White's <em>second</em> move differs from the analysis above.</p>

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

1.Ra2 g4 2.f3 gxf3 3.exf3 Ke7 4.h4 h6 5.Kf2 Kd6 6.Ke3 Ke5 7.f4+ Kf5 8.Kf2 g5 9.fxg5 hxg5 10.Bb7 Rb6 (10... Ra5? 11.Bc8+ Kf6 12.hxg5+ Kxg5 13.Bd7 Ra6 14.Rxa4 {and now black pays the price for allowing the pin}) 11.Bc8+ Ke4 12.Rxa4 Rb2+ 13.Kg1 gxh4 14.gxh4 Rb8 15.Be6 Rh8 16.Bd5+ Kd3 17.Kf2 Rxh4 18.Rxa7 Kd4 19.Kg3 Rh8 20.Kf4 Rh6 21.Rd7 Rh4+ 22.Kg5 Rh2 23.Bf7+ Ke4 24.Rd5 Rh8 25.Be6 Ra8 26.Rxc5 Rf8 27.Rd5 Ra8 {And now Stockfish announces a mate in 20+ moves, or something, lol}
</code>
</pre>
 14672: <p>In the problem position, the black player is set to liberate his rook by playing his bishop to b5 as mentioned above. Significantly, the move of the rook to a2 is the only move that forestalls black's opportunity. The tactical resource involves the linking of the white bishop and rook and is an example of coordination of pieces.</p>
 8300: <p>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.</p>

<p>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:</p>

<pre><code> [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.}
</code></pre>

<p>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.</p>
