user13147: In the below position, black is about to play 1... Bf5, developing the bishop to eventually play Nd7-Nb6.
a) Is 2. Nh4 a threat?
b) In the game Karpov-Kasparov, White played 2. 0-0 (after 1... Bf5) Nd7 3. h3 Nb6 4. g4 Bd7. Should Karpov have played 2. h3 instead?
rnb1r1k1/pp3pbp/6p1/q1pP4/8/2P1BN2/P2QBPPP/2R1K2R b K - 2 13


user11629: 
a) Is 2. Nh4 a threat?

No, because black can play 2. .. Be4 which makes the knight on h4 look a bit silly. Note that 3. f3 does not work because of 3. ... Bxd5 and if 4. Qxd5 Rxe3

b) In the game Karpov-Kasparov, White played 2. 0-0 (after 1... Bf5) Nd7 3. h3 Nb6 4. g4 Bd7. Should Karpov have played 2. h3 instead?

Probably it would lead to the same position since white will certainly want to castle sooner or later and black does not have many alternatives either.
Why do you think Karpov should have played 2. h3?

user14202: Of course it is absolutely playable -- Kasparov played it against Karpov!
2...h3 doesn't improve for White as the comments have noted.  As for Nh4 -- you are misplacing the Knight, besides Be4, Black could even play Bd7-b5.

13147: <p>In the below position, black is about to play 1... Bf5, developing the bishop to eventually play Nd7-Nb6.</p>

<p>a) Is 2. Nh4 a threat?</p>

<p>b) In the game Karpov-Kasparov, White played 2. 0-0 (after 1... Bf5) Nd7 3. h3 Nb6 4. g4 Bd7. Should Karpov have played 2. h3 instead?</p>

<pre><code>rnb1r1k1/pp3pbp/6p1/q1pP4/8/2P1BN2/P2QBPPP/2R1K2R b K - 2 13
</code></pre>
 11629: <blockquote>
  <p>a) Is 2. Nh4 a threat?</p>
</blockquote>

<p>No, because black can play 2. .. Be4 which makes the knight on h4 look a bit silly. Note that 3. f3 does not work because of 3. ... Bxd5 and if 4. Qxd5 Rxe3</p>

<blockquote>
  <p>b) In the game Karpov-Kasparov, White played 2. 0-0 (after 1... Bf5) Nd7 3. h3 Nb6 4. g4 Bd7. Should Karpov have played 2. h3 instead?</p>
</blockquote>

<p>Probably it would lead to the same position since white will certainly want to castle sooner or later and black does not have many alternatives either.</p>

<p>Why do you think Karpov should have played 2. h3?</p>
 14202: <p>Of course it is absolutely playable -- Kasparov played it against Karpov!
2...h3 doesn't improve for White as the comments have noted.  As for Nh4 -- you are misplacing the Knight, besides Be4, Black could even play Bd7-b5.</p>
