White 1…d5 is the most straightforward reply to 1 Nf3, the most flexible has to be 1…Nf6. Black still has to be careful about transpositions; 2 d4 by White leads to the position usually classified under 1 d4 Nf6 2 Nf3, and Black should be happy to play one of the defences to 1 d4 that can be reached from there. However, the move I would recommend is the flexible 2 c4, which keeps Black guessing, and is most in the spirit of 1 Nf3.
After 1 Nf3 Nf6 2 c4, Black has to be aware of the possibility that White could still play 3 d4, so his reply must not allow White to lead the game into unfamiliar territory. His most radical response is 2…c5, transposing to the Symmetrical Variation of the English Opening. This is a rich complex of openings as diverse as the Ruy Lopez or Queen’s Gambit. Please note that even if Black doesn’t play 2…c5, he can still end up in one of the lines in this variation should he play …c5 later before White has played d4.
However, not all Black players fancy playing the Symmetrical. They therefore have to choose moves consistent with their regular defences against 1 d4. The main moves to consider for Black are 2…e6, 2…b6, 2…g6 and 2…d6, although there are a few other moves that need to be taken into account.
The moves 2…e6 and 2…b6 are of most interest to adherents of the Nimzo-Indian and Queen’s Indian. The former has wider appeal, in that after 2 …e6 3 d4, we reach by transposition the line 1 d4 Nf6 2 c4 e6 3 Nf3, where Black has alternatives to the Queen’s Indian (3…b6) in 3…Bb4+, 3…c5 or even 3…d5, although if Black is happy with 3…d5, then I would suggest playing 1…d5 rather than 1…Nf6. After 2…b6, in contrast, White can pretty much force a Queen’s Indian with 3 d4, as 3…e6 is best.
I would not, however, suggest meeting either move with 3 d4, as the whole point of 1 Nf3 is to be able to avoid all those lines, and set Black problems by holding back d4; this makes it harder for him to control the key e4 square, as White can still play d3. Therefore, after 2…e6, I suggest White chooses between 3 Nc3 and 3 g3, his choice depending on whether he prefers the Queen’s Gambit (which would arise after 3 Nc3 d5 4 d4) or the Catalan (3 g3 d5 4 d4). Against 2…b6, I suggest the counter-fianchetto 3 g3, when Black needs to decide whether to go into the Symmetrical English at some point with …c5, or look for an alternative to that approach.
When Black plays 2…g6, this indicates that he is angling for either a King’s Indian or Gruenfeld. One approach for White is to play the solid fianchetto system, starting with 3 g3, and a later d4. In that case, he needs to be ready for set ups based on …d6, …d5 or even …c5.
The most aggressive continuation, and the one I have preferred, is 3 Nc3. White’s idea is to allow the King’s Indian, but avoid the Gruenfeld. If Black plays the natural 3…Bg7, White will continue with 4 e4, preventing …d5, and play will most likely continue something like 4…d6 5 d4 0-0. From this position, the varaiation I have used for many years, and the long time main line, goes 6 Be2 e5 7 0-0 Nc6 8 d5 Ne7 9 b4.
If Black tries 3…d5, hoping for 4 d4 and the Gruenfeld, White can adopt one of several approaches based on delaying, and perhaps even omitting d4. The one I have tended to use starts with the disruptive check 4 Qa4+. The most natural reply for Black is 4…Bd7, when playing will most likely continue with 5 Qb3 dxc4 6 Qxc4. After 6…Bg7, the line 7 e4 0-0 8 e5 illustrates the advantages both of delaying d4 and of forcing the Black bishop onto d7; White has been able to play e5 one move earlier than he normally would, since he has not played d4, while Black has to choose between g4 and e8 for his knight, because the bishop is on d7.
A move related to 2…g6 is 2…d6. This has the immediate threat of 3…e5, which White should meet with 3 d4. Black then needs to decide whether to play a normal King’s Indian with 3…g6 4 Nc3 Bg7 5 e4, or aim for an independent set up with 3…Nbd7, 3…Bg4 or 3…Bf5. These systems, usually referred to as the Old Indian, are not popular among top level players, but they are not without bite, so White needs to be prepared for them.
Black can also play 2…Nc6, if he wants to angle for …e5. Just as with 2…d6, I recommend that White prevents this with 3 d4. Then Black’s usual move is 3…e6, against which I would play 4 a3, preventing 4…Bb4, and waiting to see whether Black aims for a system based on …d5 or …g6.
The above is meant to be an overview of the main Black systems. I shall be looking at the various Black possibilities in detail in subsequent posts.