I'd say that in the Classical Scheveningen, Nb3 is typically a response to ...Bd7, avoiding ...Nxd4 plus ...Bc6 and trying to cause Black some discomfort from the bishop's position (e.g. having to move it again if he wants to meet g4 and g5 with ...Nd7).

Kasparov talks about how was prepared to play e5 line  in first world championship line,  in his books. Karpov played g4 anyway without Nf6. It's relatively rare these days because white didn't find anything much against it. A similar position in be2 e5 Nadjorf early f4 ideas for white have been neutralised with e5xf4 etc.

RdC wrote on 06/05/14 at 22:32:38:


But with a Najdorf move order (which was usually the case with Kasparov as far as I know), the 9...e5 line isn't an option.

The a3 Sozin does seem a possibility here (not to be confused with the a4 Sozin which has been favored by John Emms ...).  Incidentally reminds me of a fairly recent game which struck me as rather thematic-looking, between GM Saltaev and IM Hoeksema in the Dutch league.

kylemeister wrote on 06/05/14 at 19:42:54:

This 9...,e5 line was already discussed earlier on chesspub, see http://www.chesspub.com/cgi-bin/yabb2/YaBB.pl?num=1333369435/2

TN wrote on 06/05/14 at 13:10:21:


Kylemeister's line looked interesting, using the tempo gain to move from a Scheveningen structure to a Boleslavsky one. In fact there's a handful of games where Black has tried playing e5 after first playing e6 in main lines, but it's hardly a mainstream idea. A game in 1995 at the Donner Memorial between Judit Polgar and Granda Zuniga is one high level example. It used to be said that Granda Zuniga either didn't know or just ignored theory.

That is the line in my repertoire today against the Grivas.
It is very dangerous for black. A recent example was shown a few days ago on chessvibes: http://www.chessvibes.com/?q=my-second-im-norm in which the famous writer Doggers defeated the Italian IM Bruno Fabio. However he didn't insert a3. I didn't check in detail but his own analysis of move 10 hint that a3 could be necessary.

In a recent game, I faced the Grivas Sicilian. This went 1. e4 c5 2. Nf3 Nc6 3. d4 cxd4 4. Nxd4 Qb6 5. Nb3 e6 . Here I became concerned about Bb4 ideas but decided to allow them. The game continued 6. Be3 Qc7 7. Nc3 Nf6 8. Be2. Black now elected to go into a Sicilian Hedgehog formation with 8. .. d6. But 8. .. Bb4 is also playable and may be advantageous to Black. Apparently theory is that White should prevent the pin with a3 at some relevant stage.

This reminded me of a line I was aware of, forty-five years ago, that in the sequence 1. e4 c5 2. Nf3 e6 3. d4 cxd4 4. Nxd4 Nf6 5. Nc3 Nc6, it was possible to play 6. a3. 6. Ndb5 has always struck me as a move that you would only play if you knew and trusted established theory. Should Black responded to 6. a3 with 6. .. d6, you are in a Scheveningen, possibly with an extra tempo for Black. So perhaps 6. a3 in that move order is still viable on the grounds that tempi aren't that relevant to Hedgehog style defences.