user45: The following tactics problem is problem #97369 from ChessTempo. It is a position from a game between Yuri Yakovich and Pavel Kotsur. It's black's move.
The idea of the tactics problem is to find black's best move from the shown position.
But my question is slightly different: If both players play perfectly from the position shown in the diagram, can black force a win, or can white force a draw?
[FEN "6k1/5p2/1Pp3pb/2q4p/1rNpPP2/3Q2PP/8/5RK1 b - - 0 1"]

I tried using a couple of chess engines to analyze the position. The lines they suggested gave black a positive score, but didn't seem to give a forced win.
So what do you think: is it a theoretical win for black or can white escape with a draw?

user70: To answer your question directly, I don't think this is a theoretical win or draw.  The reason is that the game is still too up-in-the-air.  There may be a forced win for one side or the other, but that's not the same thing.

user45: I think it's a forced win for black.
Black can start with 1...Qxc4 after which the next five white moves are forced to avoid a fast loss.
[FEN "6k1/5p2/1Pp3pb/2q4p/1rNpPP2/3Q2PP/8/5RK1 b - - 0 1"]

1...Qxc4 2.Qxc4 Rxc4 3.Rb1! Bf8! 4.b7! (4.e5!? d3 5.b7 d2 6.b8=Q Rc1+ 7.Kf2 d1=Q) Bd6! 5.b8=Q+ Bxb8 6. Rxb8+ Kg7

Black is a pawn up and has connected passed pawns and should try to exchange pawns to simplify to a won end-game. The game might continue for example as follows:
[FEN "1R4k1/5p2/2p3p1/7p/2rpPP2/6PP/8/6K1 b - - 0 6"]

6... Kg7 7.e5 c5 8.Rd8 Rc3 9.Kf2 h4! 10.gxh4 Rxh3 11.Rc8 Rc3

The computer still doesn't find a line that leads to an obvious win but it looks like a hopeless situation for white and the computer playing against itself gives a win for black. Here's an example way to continue the game:
[FEN "2R5/5pk1/6p1/2p1P3/3p1P1P/7r/5K2/8 b - - 0 11"]

1... Rc3 2. Rc7 Kf8 3. Ke2 c4 4. Kd2 Rf3 5. Rxc4 Rxf4 6. Rc8+ Kg7 7. Rc7 Re4 8. Re7 Rxh4 9. e6 Kf6 10. Rxf7+ Kxe6 0-1

The final position is a table base win for Black.
If you think there any errors in this analysis (in particular, weak moves for white that changed the value of the position from drawn to lost) then please let me know.

45: <p>The following tactics problem is <a href="http://chesstempo.com/chess-problems/97369" rel="nofollow noreferrer">problem #97369 from ChessTempo</a>. It is a position from a <a href="http://chesstempo.com/gamedb/game/1155017/6k1/5p2/1Pp3pb/2q4p/1rNpPP2/3Q2PP/8/5RK1%20b%20-%20-%200%2040&amp;flip=true" rel="nofollow noreferrer">game between Yuri Yakovich and Pavel Kotsur</a>. It's black's move.</p>

<p>The idea of the tactics problem is to find black's best move from the shown position.</p>

<p>But my question is slightly different: If both players play <em>perfectly</em> from the position shown in the diagram, can black force a win, or can white force a draw?</p>

<pre><code>[FEN "6k1/5p2/1Pp3pb/2q4p/1rNpPP2/3Q2PP/8/5RK1 b - - 0 1"]
</code></pre>

<p>I tried using a couple of chess engines to analyze the position. The lines they suggested gave black a positive score, but didn't seem to give a forced win.</p>

<p>So what do you think: is it a theoretical win for black or can white escape with a draw?</p>
 70: <p>To answer your question directly, I don't think this is a <em>theoretical</em> win or draw.  The reason is that the game is still too up-in-the-air.  There may be a forced win for one side or the other, but that's not the same thing.</p>
 45: <p>I think it's a forced <strong>win for black</strong>.</p>

<p>Black can start with <code>1...Qxc4</code> after which the next five white moves are forced to avoid a fast loss.</p>

<pre><code>[FEN "6k1/5p2/1Pp3pb/2q4p/1rNpPP2/3Q2PP/8/5RK1 b - - 0 1"]

1...Qxc4 2.Qxc4 Rxc4 3.Rb1! Bf8! 4.b7! (4.e5!? d3 5.b7 d2 6.b8=Q Rc1+ 7.Kf2 d1=Q) Bd6! 5.b8=Q+ Bxb8 6. Rxb8+ Kg7
</code></pre>

<p>Black is a pawn up and has connected passed pawns and should try to exchange pawns to simplify to a won end-game. The game might continue for example as follows:</p>

<pre><code>[FEN "1R4k1/5p2/2p3p1/7p/2rpPP2/6PP/8/6K1 b - - 0 6"]

6... Kg7 7.e5 c5 8.Rd8 Rc3 9.Kf2 h4! 10.gxh4 Rxh3 11.Rc8 Rc3
</code></pre>

<p>The computer still doesn't find a line that leads to an obvious win but it looks like a hopeless situation for white and the computer playing against itself gives a win for black. Here's an example way to continue the game:</p>

<pre><code>[FEN "2R5/5pk1/6p1/2p1P3/3p1P1P/7r/5K2/8 b - - 0 11"]

1... Rc3 2. Rc7 Kf8 3. Ke2 c4 4. Kd2 Rf3 5. Rxc4 Rxf4 6. Rc8+ Kg7 7. Rc7 Re4 8. Re7 Rxh4 9. e6 Kf6 10. Rxf7+ Kxe6 0-1
</code></pre>

<p>The final position is a table base win for Black.</p>

<p>If you think there any errors in this analysis (in particular, weak moves for white that changed the value of the position from drawn to lost) then please let me know.</p>
