user14511: After 1. e4 c5 2. Nf3 Nc6 3. d4 cxd4 4. Nxd4 e5 why is 5. Nb5 the best move?
The game usually continues 5. Nb5 d6 6. N1c3 a6 7. Na3 and it looks to me like whites knight on a3 is misplaced. What makes this line good for white?


      [StartPly "8"]

      [FEN ""]
      1.e4 c5 2.Nf3 Nc6 3.d4 cxd4 4.Nxd4 e5 5.Nb5 d6 6.N1c3 a6 7.Na3




user2174: The knight has been recluded to the a3 square, with the move a6 and e5. while a6 may be a useful tempo, e5 is weakening. Meanwhile, the knight is going to e3 via c4, controlling d5. If black plays b5 to avoid it, then white ideas are based on the c4 break: in this case, the Knight can be recycled via c2.

user4362: The real reason why this is the main line lies in the many possible variations after 5.Nb5 and its alternatives. Any verbal explanation will at best be approximately correct. With that in mind, here is my take:
5.Nb5 is the variation that best keeps control of the weakened d5 square. If black achieves d5 its only strategic problem will vanish, so keeping control of d5 is whites main strategic objective. 5.Nb5 provokes d6, which makes it impossible for the Nc3 to be neutralised by Bb4. This Bb4 move is a problem if the knight retreats to f3 or b3. If the knight goes to f5, d5 is even immediately possible.

14511: <p>After 1. e4 c5 2. Nf3 Nc6 3. d4 cxd4 4. Nxd4 e5 why is 5. Nb5 the best move?
The game usually continues 5. Nb5 d6 6. N1c3 a6 7. Na3 and it looks to me like whites knight on a3 is misplaced. What makes this line good for white?</p>

<pre>
<code>
      [StartPly "8"]

      [FEN ""]
      1.e4 c5 2.Nf3 Nc6 3.d4 cxd4 4.Nxd4 e5 5.Nb5 d6 6.N1c3 a6 7.Na3

</code>
</pre>
 2174: <p>The knight has been recluded to the a3 square, with the move a6 and e5. while a6 may be a useful tempo, e5 is weakening. Meanwhile, the knight is going to e3 via c4, controlling d5. If black plays b5 to avoid it, then white ideas are based on the c4 break: in this case, the Knight can be recycled via c2.</p>
 4362: <p>The real reason why this is the main line lies in the many possible variations after 5.Nb5 and its alternatives. Any verbal explanation will at best be approximately correct. With that in mind, here is my take:</p>

<p>5.Nb5 is the variation that best keeps control of the weakened d5 square. If black achieves d5 its only strategic problem will vanish, so keeping control of d5 is whites main strategic objective. 5.Nb5 provokes d6, which makes it impossible for the Nc3 to be neutralised by Bb4. This Bb4 move is a problem if the knight retreats to f3 or b3. If the knight goes to f5, d5 is even immediately possible.</p>
