user26187: 
Why is it that ng4 is the best move here? I played f4

user15478: It is a pretty forcing move, White does not have many options to react to it and all are painful.
The most obvious question, why cannot White take?
Because hxg4 Rh8+ is forced mate.
If Rook takes we just take Back, White has no meaningful checks and we are just up a rook.
Finally, if White dodges with Kh1 we take the knight, and White still cannot take ours due to Rh8+ being devastating.
[Variant "From Position"]
[FEN "r3r3/p1p3k1/1b6/5pN1/Q1Pp2n1/P2Pq2P/1P2P1RK/R7 w - - 0 1"]

1. Kh1 (1. hxg4 Rh8+ 2. Nh3 Rxh3#) (1. Rxg4 fxg4 2. Qd7+ Re7 3. Qxg4 Qxe2+ 4. Kg1 Qxg4+
5. hxg4)Qxg5 2. hxg4 Rh8+ 3. Kg1 Qe3+ 4. Rf2 Rh2


26187: <p><a href="https://i.stack.imgur.com/VKDAn.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/VKDAn.jpg" alt="Ng4+ vs f4" /></a></p>
<p>Why is it that ng4 is the best move here? I played f4</p>
 15478: <p>It is a pretty forcing move, White does not have many options to react to it and all are painful.</p>
<p>The most obvious question, why cannot White take?</p>
<p>Because hxg4 Rh8+ is forced mate.</p>
<p>If Rook takes we just take Back, White has no meaningful checks and we are just up a rook.</p>
<p>Finally, if White dodges with Kh1 we take the knight, and White still cannot take ours due to Rh8+ being devastating.</p>
<pre><code>[Variant &quot;From Position&quot;]
[FEN &quot;r3r3/p1p3k1/1b6/5pN1/Q1Pp2n1/P2Pq2P/1P2P1RK/R7 w - - 0 1&quot;]

1. Kh1 (1. hxg4 Rh8+ 2. Nh3 Rxh3#) (1. Rxg4 fxg4 2. Qd7+ Re7 3. Qxg4 Qxe2+ 4. Kg1 Qxg4+
5. hxg4)Qxg5 2. hxg4 Rh8+ 3. Kg1 Qe3+ 4. Rf2 Rh2
</code></pre>
