Recently a game was published in an article that included the following position:

This was called the Benko gambit. The position came about through a different move order than the usual Benko, but I have no problem calling this the Benko gambit.

In the typical Benko (1. d4 Nf6 2. c4 c5 3. d5 b5) black gambits the pawn on b5 before white plays Nc3 and therefore Nxb5 is not an option. In the position above, white could play Nxb5. The annotator's notes to white's 8. cxb5 were simply "No other move really tests Black's dynamic choice."

I'd like to hear what people think about the possibility of 8. Nxb5 in the above position.

Nxb5 Qa5+ is good for Black.

What about Nxb5 Qa5+ Nc3 Ne4, looks pretty good for black.

if you ask me Nxb5 is not very good because it gives black e4 say 8...Ne4 and g5 is looking good for black even after say 9.Qc2 Qa5+ not say this wins for black but i think 8.cxb5 is better

I feel that it must have something to do with white's dark squared bishop being off the c1-h6 diagonal, and something like 8. Nxb5 Qa5+ 9. Nc3 Ne4 clearly takes advantage of this, but white can play 8. Nxb5 Qa5+ 9. Qd2 and it looks like he's not in any trouble. So I'm not sure that 8. ... Qa5+ is the refutation to 8. ... Nxb5.

After 8. Nxb5 Ne4 then 9. Qc2 defending b2 and attacking the e4 knight looks ok.

8. Nxb5 Ne4 9. Qc2 Qa5+ 10. Kd1 f5

Black looks good.

slack, why play 10. Kd1 instead of 10. Nd2. Of course black has an initiative in this position, but unless it comes to something white is going to play e3, Bd3 and 0-0 and have an extra pawn.

I suppose after 8.Nxb5 Ba6 9.a4 Bxb5 10.axb5 (cxb5 looks worse) a6 black has typical benko compensation, only he has traded off his white bishop (which often gets in the way of his queenside play in the accepted lines) for blacks valuable knight. White's queenside will be weaker than usual.

FYI, I think black's kingside rook is misplaced

I don't think there's anything "wrong" with Nxb5, maybe it's just not as good as cxb5? I don't know. Maybe the book move is the more active choice and would therefore test black more?

Forgot about Nd2, haha. :)

9. ..Qa5+ 10. Nd2 a6 11. Qxe4 axb5 12. Bxe7 Re8 13. Bxc5. Garbage.

with Nxb5, white allows black to develop quicker on that flank.  a pawn on b5 blocks the storm more easily.

ericmittens, at the end of your line, black is not threatening axb5 since the a-pawn is pinned. So it's white who gets some typical Benko action by playing d6 and creating long term play on the d-file, and quarantining the knight at b8 for a bit.

Ahh yes you're right...hmmm...

What about Qb6 followed by a6?

loomis: the more I look at this the more I see your points about it. 

My hyper reactive move Qa5+ does not seem to be the best path for black, no doubt.  But, I do not think there is a "refutation" to be had here so much as white being able to keep a more comfortable edge with cb than with Nxb5.

For instance, in the line above given w/ 8. Nxb5 Ne4 9. Qc2 Qa5+ 10. Kd1 f5 White plays 11. g4 and keeps a good edge.  I also think santiR point about shutting down potential counterplay on the b file might be accurate as well, so that it is really a more long term strategic decision made by a GM with experience than it is a matter of direct tactical refutations.

I think.

I'm not so sure that Qc2 solves white's problem.  After 8...Ne4 9.Qc2 Qa5+ 10.Nd2 a6!? 11.Nc3 Nxc3 white's stuck with a couple of very annoying doubled pawns and a long-term problem.  To make matters worse, the pawn on c3 is under heavy pressure from the queen and g7 bishop and requires immediate defensive support.  I see nothing but trouble ahead for white....

11.Qxe4 axb5 doesn't really work because of Bxb2.  The weak b2 pawn hampers whites options or so it seems.

[Edit: My apologies slack, I hadn't realized you'd posted this line previously.  I'm impatient like that. ]

Ahhh Gonnosuke, so good of you to come support my favorite opening 

Very interesting topic! 

It drives me nuts when I come across vague annotations that sound oh so certain in their conclusion but completely fail to address an obvious or natural looking move.  Nxb5 is the perfect example -- logical and obvious with no clear refutation anywhere in sight!

Gonnusuke, I missed the b2 weakness. Originally I thought after 11. Qxe4 axb5 white would be able to take on e7 as suggested by slack. But maybe going back to c2 12. Qc2 is fine for white since Bxe7 is still threatened. It doesn't seem like black can put anything together tactically since only the queen and bishop are developed. White is still hoping to play e3, Bd3, and 0-0 with a good game.

I think the conclusion that cxb5 is a well known Benko structure where white knows his long term strategic goal may have been the motivating factor behind taking with the pawn instead of the knight. Clearly there are complexities in the position after Nxb5 that white might have felt black was better prepared for, this is after all an unusual move order for black to choose to play the Benko.

I'm inclined to agree.  If given a choice between the familiar or the unfamiliar, it's a no-brainer.  When viewed through that lens, cxb5 really is the only viable continuation. 

But it doesn't make Nxb5 any less interesting from a theoretical standpoint!  Who knows what you'll find once you start digging....

Your idea with Nxb5 is very interesting to investigate, but your strategical evaluation is little incorrect. Black actually already well developed. He already castled, he has safe king and can make every next move with agressive direct threats with no caution, his rook h8 already get freedom and waiting to strike at any line and all other pieces can join the battle very quickly. While white need a lot of moves to be able to castle, and he cant make this moves so easy because black threating with every move, h1 rook is buried for long time and f1 bishop is very passive, because it cant threat to black (yet) and also cant protect black squares in whites camp, while white should spend time to move it anyway. And the main - white king is exposed and vulnerable. That is more correct evaluation, so black has total and sound compensation for a pawn and position is dynamically even (or around, no more than += theoretically). About rest i agreed with b2 problem and with what Gonnosuke said. Also there was sad that game was in rapid time control, so when you look at Nxb5 and see you exposed your b2 pawn - that is enough to start warry, because in rapid you want to stick with known lines and avoid of spending too much time for such problems.