Why 5...a6 in the Sicilian Najdorf?

For this forum I would like to discuss the position after 1.e4 c5 2.Nf3 d6 3.d4 cxd4 4.Nxd4 Nf6 5.Nc3 in the Sicilian.I have had a few games recently where black does not play 5...a6 and instead plays something like 5...Nc6, 5...e6 or 5...g6. Considering the popularity of the move a6, I figure there is reason for it, but in none of the games I played did I feel I was able to exploit the fact that my opponent did not play a6, so I am wondering exactly why 5...a6 is so important, and more specifically, if black does not play 5...a6, how should white try to exploit that?

Hello Sean,

I don't play the Najdorf variation much, but I do know some of the main ideas from this line. 5...a6 is very much a prophylactic move, meaning that it serves to prevent the opponent from making certain moves. 5...a6 stops both white's knights and bishop from occupying b5. It's a sound defensive move and has been utilized by the highest chess minds over the years. As far as exploiting black's position after a move other than 5...a6, take a look at this line out of the Yugoslav Attack stemming from the Sicilian Dragon variation:

I actually just found this line after looking at a video on the Sicilian Dragon and have never employed it but it looks like something worth experimenting with.

I'm going to look into more ways white can capitalize after move 5 of the Sicilian. I'll keep you updated.

- Charles

It stops a knight or bishop coming to b5.
It prepaires a later b5 which is the beginning of a queenside attack.
And it also is kind of a waiting move to see what white wants to do.
And blacks position is just more flexible. The c6 square is not always the best for the knight in the sicilian, black keeps the option of playing Nd7 which is played in the najdorf most of the time. (In the classical variation black plays an early Nc6)

From the French Defense, I know that Black almost always sneaks in a a6, to keep a Knight off b5 (and also to prop up a future ...b5 push to expand), since a Knight on b5 can plop down on d6 when there is a White pawn on e5. In the Sicilian, when Black has played e5, the knight usually goes to b3 but, depending on the timing, it can go to b5 with advantage, especially if White has already played Qd2 and 0-0-0. In another sense, a6 can be a useful "pass" move, giving White a move to reveal intentions and allowing Black to figure the best position of the Bishops (e7 and e6 or e7 and b7).

All of those moves are perfectly good.

If you'd like some examples of what can potentially happen when Black omits ... a6, try this:

I find that explanation completely unconvincing.

White's advantages against the Sicilian are largely due to his space advantage and his superior development, which offers prospects of attack and combination play.

An exchange of pieces is antithetical to those advantages. Both space advantage and combination play are best pursued on a crowded chess-board, not on a half-empty one.

Black wants to play e5 but if black plays it immediately white has Bb5+ (The Venice Attack). If bishop blocks then Bxd7 followed by Nde2. Black will never be able to play d5 as they have no bishop covering that square and d5 will permanently be a hole that white can exploit.

After 6. Bb5+ Bd7 7. Bxd7 Qxd7, 8. Nf5 is not really good as black has the tactic Nxe4.

After 6. Bb5+ Nbd7, then Nf5 is preferred as the tactic can't be played immediately and white can play Bg5.

7. Nf5 a6 8. Bxd7 has been played most often but I think 7. Nf5 a6 8. Ba4 b5 9. Bb3 is better as it reroutes the bishop to a square where it controls d5.

All of white's pieces are pointed at d5. Black can play on and the engine will give only about +0.7 but the reality is that it's much more difficult and unpleasant to play for a human player.

There are specific lines that people say give white an advantage, but it's not actually about the specific lines. It's more about the d5 weakness and how it can be exploited. In some moment, white will want to play Bg5 and trade off bishop for the f6 knight, leaving d5 terminally weak.

This is why in the Bg5 Najdorf, black can't play e5 either as Bg5 renews the prevention of e5. This is a common mistake for those who don't know anything about the Najdorf.

White has a bind on the position as the d5 knight can never be kicked and even the f5 pawn restrains some of black's counterplay with f5 like in the Sveshnikov.

That's why e6 or Nbd7 are played instead.

Against Nbd7, Bc4 is normally played as Nbd7 still retains the option of e5 in some lines.

Bg5 and Bc4 are the only moves in the Najdorf where you can't play e5 against them as they control d5. As said before, black can play on but no-one wants to play that type of position with black as they are helpless on the d5 hole.

Against pretty much every other move against the Najdorf, e5 is the most popular.

This video explains it all very well.

Just the usual explanation.

First consider the position on move 5:

White will have advantages in space and development, but in order to gain those advantages he had to give up a center Pawn in exchange for a flank Pawn (3. d4 cxd4 4. Nxd4). That leaves Black with two center Pawns against one... which in turn means that the e4 Pawn is going to be one of the most critical targets in White's position. It's his LAST center Pawn, after all.

The move 5. ... a6 accomplishes multiple goals at the same time. It prevents a Bishop-check on b5, and also prevents a White Knight from landing on that square. Without a Pawn on a6, the c7 square would not be a safe post for Black's Queen. See Fischer - Tal, Bled 1961.

Fischer vs Tal (1961) Bled (365chess.com)

The a7-a6 move also directly supports a follow-up b7-b5 Pawn move, which again offers multiple paths forward for Black. It clears the b7 square for Black's Bishop, to enable Bb7 taking aim at White's vulnerable e-Pawn. The b5 Pawn itself supports a powerful Knight outpost on c4 (Nb8-d7-b6-c4) and alternatively it threatens to push onward to b4, unhinging the c3-Knight that protects the important Pawn on e4.

Was my explanation not convincing? Lol. I put some time into that. In almost every Sicilian, black plays a6 at some point. Not only does it prevent Bb5+ and Nb5, it also prepares b5-Bb7.

Ah ok, no worries. I did go fairly in depth into some lines. Good luck in your studies!

Ndb5 and Bb5 are often thematic moves in Sicilian positions, so a6 serves a triple function. It defends the b5 square, allows for b5 to be played in the future, and it also serves as a fantastic waiting move to see how White will attempt to progress the position.
The other four good moves in the position (5... g6 Dragon, 5... e6 Scheveningen, 5... Nc6 Classical, and 5... e5) all have unique weaknesses, 5... a6 has all the advantages listed above, but Black can also avoid unfavorable lines and still play one of these moves later (for example, Black can avoid the Keres Attack in the Scheveningen by simply delaying e6 for a move, forcing White to play a more general developing move).

The point about Bb5 being significant is correct, but the positional explanation about the scope of the bishop misses the point.  It's more concrete than that.

The point of a6 is to be able to play e5 without running into a specific problem which results from Bb5+, which is that Black has to block the check by sticking a piece on d7 and thereby prevents the c8 bishop from controling the f5 square. This allows White's d4 knight to respond to e7-e5 by *improving* itself with a jump to f5, rather than retreating to b3 or f3.  Here's the problem:

There are other reasons 5. .... a6 is good -- it's a flexible move you'll likely need at some point; it lets you wait and see White's plan before choosing between e7-e6 and e7-e5, etc.  But this concrete problem is the biggie you need to know about.  Incidentally, the three other move you mentioned you sometimes see are all good moves partly because they solve it in their own ways.  e6 and g6 simply don't allow Nf5 (and they don't aspire to play e5 anyway), whereas Nc6 solves the problem at least for now because it means Bb5 doesn't come with check.

So this doesn't really help you punish the alternatives to a6 that you've been seeing (since those are all good moves), but it will help you if you ever run into the dubious 5. ... e5.

Why are you insisting on the inferior move 7. ... Nbxd7?

If Black plays 7. ... Qxd7 instead, then 8. Nf5 Nxe4! is dead equal (as in: 0.00).

Oops.  I completely skipped past SamuelAjedrez95's post, which both covers part of what I tried to say, but also, importantly, corrects me on some key points.  I'd completely forgotten about that Nxe4 idea.  It seems I needed this refresher, for which much thanks.

In short, what he said, not what what I said (except to the extent they overlap).

It's back now. That video by Andras Toth was very helpful in explaining the Sicilian in general from the perspective of many different variations as it's a general rule.

e5 shouldn't be played when Nf5 is good. Nf5 is good when black can't play d5. If Nf5 is played when it isn't good, d5 should be played.

There are some complications in each individual case but it's basically something like this.

We can see some examples.

If white plays Nf5 in the English Attack.

White is in trouble here. This is where we see the notorious Sicilian pawn centre shine.

If white plays Nf5 against the Sveshnikov.

This endgame is considered to be very pleasant for black as they are way better developed.

Alternatively, if black plays e5 when d5 can't be played then Nf5 does work, like against Bc4.

d5 can't be played because it would just be taken and otherwise black just has glaring holes on the light squares.