It's hard to believe that such an insipid move as 5...a6 would have so much theory woven around it. Today's chess history: When this was first introduced 60 or so years ago, the intent was to prepare not ...b5, but ...e5! The point of ...a6 was to take away the b5 square from the N on d4. This was considered an improvement to the classical Boleslavsky variation (1.e4 c5 2.Nf3 Nc6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 d6 6.Be2 e5), as the N on b8 can often be more effective on d7 than on c6. So in a sense this is a "high-class waiting move."

Mind you, you could argue that the possibility of ...b5 is a by-product of preparation for the central thrust of the e-pawn. Meanwhile, White replies to this with 6.Be3, a move in its relative infancy when I was playing, back in the '80s. Theory tended to support 6.Bg5 or 6.Bc4 as the most aggressive tries, though there were plenty of other possibilities as well (6.Be2, 6.f4, even 6.h3!?).

Or Rg1

6.Be3 is the latest try by white to deal with the Najdorf, popularized in the 1980's and 1990's by various English players, hence its name (English attack). An interesting try by black here is 6...Ng4!?, trying to immediately exploit white's 6th move.

Professor Unwin: 'Are you all sitting comfortabold two-square on your botty? Then I'll begin...' See the Small Faces' LP and CD 'Ogden's Nut Gone Flake'.

Bxb3 is *not* forced. Black can also play 15...a4!?, entering an extremely sharp (and unclear) position.

The threat of Nxb3+ is stronger than Nxe4+ because of the double check it provides and forcing movement of the king. White can follow Nxe4+ with Qc2.

The "correct" move is 16...a4. Black needs to open up lines to white's K before white does the same thing on the other side of the board. 16...Nc5? allows white to seal up the c-file with a subsequent, well-timed Bxc5, retarding black's Q-side attack, for example 17.Ng3 a4 18.Bxc5

Now it's too late for ...a4, white's attack gets there first. In these kinds of positions with the players attacking on opposite flanks, every tempo is critical. Black is lost now.

White can eliminate all counter-play by playing 21.Bxc4 first, then Nh5, but 21.Nh5 right away is also good enough to win.

And remains taboo.

Nf5+ leads to mate after either Qg7 Qxg7# or Kg8 Nh6# also forking king and queen

I agree with dessertfox, except that I was thinking of 28...Kg8 29.Ne7#  

White seems to have a large choice here. This move is good; but equally decisive are 28.Rg1 and 28.Be2