user3273: [FEN "rnbqkb1r/pp4pp/2p1pn2/3p1p2/3P4/BP4PN/P1P1PPBP/RN1QK2R b KQkq - 0 1"]
[StartFlipped "0"]

1... Bxa3 2.Nxa3 Qa5+ 3.Kf1 Qxa3

FEN: rnbqkb1r/pp4pp/2p1pn2/3p1p2/3P4/BP4PN/P1P1PPBP/RN1QK2R b - - 0 1
I thought that the solution would be equivalent to 1... Qa5+ 2. Kf1 Bxa3 3. Nxa3 Qxa3. But apparently, my solution is wrong. What is the difference between these two sequences? Why should you take the White bishop first?

user12629: The answer was given in a comment:

After your Qa5+ how do you make White play Kf1? What do you do if he plays Qd2?

This is correct. There's really nothing you can do after Qa5+ Qd2 that gives Black a significant advantage.

He can play Qd2 after Bxa3; Nxa3 Qa5; too right?

White can play that, but it doesn't help in that position. You can take the knight with your queen. (If you played Qa5+ first, then ...Qxa3 loses to Nxa3, and ...Bxa3 is obviously responded to with Qxa5.)
[FEN "rnbqkb1r/pp4pp/2p1pn2/3p1p2/3P4/BP4PN/P1P1PPBP/RN1QK2R b KQkq - 0 1"]
[startflipped ""]

1... Bxa3 (1... Qa5+ 2. Qd2 Qxa3? (2... Qxd2+ 3. Kxd2 Bxa3 4. Nxa3 {Material is even.}) (2... Bxa3 3. Qxa5 Bb2 4. Qb4 Bxa1 {Rook and bishop for the queen for now, although Black's bishop may get trapped. Certainly White has the advantage.}) 3. Nxa3 Bxa3 {Two pieces for the queen; White is clearly ahead.}) 2. Nxa3 Qa5+ 3. Qd2 Qxa3 {Black is up a knight.}


3273: <pre><code>[FEN &quot;rnbqkb1r/pp4pp/2p1pn2/3p1p2/3P4/BP4PN/P1P1PPBP/RN1QK2R b KQkq - 0 1&quot;]
[StartFlipped &quot;0&quot;]

1... Bxa3 2.Nxa3 Qa5+ 3.Kf1 Qxa3
</code></pre>
<p>FEN: rnbqkb1r/pp4pp/2p1pn2/3p1p2/3P4/BP4PN/P1P1PPBP/RN1QK2R b - - 0 1</p>
<p>I thought that the solution would be equivalent to 1... Qa5+ 2. Kf1 Bxa3 3. Nxa3 Qxa3. But apparently, my solution is wrong. What is the difference between these two sequences? Why should you take the White bishop first?</p>
 12629: <p>The answer was given in a comment:</p>
<blockquote>
<p>After your Qa5+ how do you make White play Kf1? What do you do if he plays Qd2?</p>
</blockquote>
<p>This is correct. There's really nothing you can do after Qa5+ Qd2 that gives Black a significant advantage.</p>
<blockquote>
<p>He can play Qd2 after Bxa3; Nxa3 Qa5; too right?</p>
</blockquote>
<p>White can play that, but it doesn't help in that position. You can take the knight with your queen. (If you played Qa5+ first, then ...Qxa3 loses to Nxa3, and ...Bxa3 is obviously responded to with Qxa5.)</p>
<pre><code>[FEN &quot;rnbqkb1r/pp4pp/2p1pn2/3p1p2/3P4/BP4PN/P1P1PPBP/RN1QK2R b KQkq - 0 1&quot;]
[startflipped &quot;&quot;]

1... Bxa3 (1... Qa5+ 2. Qd2 Qxa3? (2... Qxd2+ 3. Kxd2 Bxa3 4. Nxa3 {Material is even.}) (2... Bxa3 3. Qxa5 Bb2 4. Qb4 Bxa1 {Rook and bishop for the queen for now, although Black's bishop may get trapped. Certainly White has the advantage.}) 3. Nxa3 Bxa3 {Two pieces for the queen; White is clearly ahead.}) 2. Nxa3 Qa5+ 3. Qd2 Qxa3 {Black is up a knight.}
</code></pre>
