I think that was his intention all along. It's not clear, though, that ...a6 was much of a loss of time for Black.

Yes - I can hardly start King side action until he has committed his king to that side

@jkarp: he means an attack that looks like the Black attack in the King's Indian defence. Black often plays ...f5 somewhere around move 10-15 in that opening.

You just removed a defender of that square, so it's now easier for a knight to jump into and remain on that square.

I might have been inclined to play 13.f4 instead...

f4 is best by not giving up the center but fight for it

I thought that must be on the agenda somewhere...

White also blocks conection of Queen and Bishop.

The annotator means that he develops the rook that was not very active.

It is not a bad practice, when you find yourself with nothing much to do, and there's nothing on - in quiet positions, in other words - to see if you can't improve the position of your least active or useful piece. The one that isn't really doing much for your game. Black decided that the Queen's Rook wasn't doing much of anything on a8, and so moved it somewhere handier. The other rook he kept on the f-file as things are likely to happen on that file.

Usually in this positions play Rab1

There is pressure on d5, Joe, though it's not especially heavy. All the same, with 2 pieces attacking the Knight on d5, White has to maintain at least a 2-man defence.

jkarp, look at the position. Black has three pieces attacking the knight on d5. A knight, a bishop and a queen. Right now, black is threatening to win a pawn as white only has two pieces defending the knight.

looks like the bishop would have been better than the knight!?

This is the same Bishop that was entombed a little while before.

@jkarp: now that his knight is threatened, it has to move away, and then Bxb7 could become a problem.