user29957: I can't, for the life of me, figure out how to solve this puzzle. White to move.
  [FEN "r5k1/6p1/1pp2p1p/p2n1q2/3Q4/P4PB1/2P3PP/4R1K1 w - - 0 1"]


user28439: c4 is the answer. Threaten the knight and it has no squares to go to. All squares it can go to are either under control by white or blocked by black pieces (f4 is protected by black queen but f4 is double attacked by white bishop and queen). You win the black knight.

29957: <p>I can't, for the life of me, figure out how to solve this puzzle. White to move.</p>
<pre><code>  [FEN &quot;r5k1/6p1/1pp2p1p/p2n1q2/3Q4/P4PB1/2P3PP/4R1K1 w - - 0 1&quot;]
</code></pre>
 28439: <p>c4 is the answer. Threaten the knight and it has no squares to go to. All squares it can go to are either under control by white or blocked by black pieces (f4 is protected by black queen but f4 is double attacked by white bishop and queen). You win the black knight.</p>
