This is the classic move order in TDKS against 1. e4, the Nimzowitsch Defence. Until the 1980s it was considered clearly inferior, and as in real life, a bad reputation lasts longer than it is justified. Good for Black, because in the three variants resulting from the diagram position there are enough resources for a successful game.
White has the choice between 3. e5 (the advance variation), 3. exd5 (the exchange variation) and 3. Sc3 (the alleged refutation of the entire black structure). Let’s start with the latter, because if this were indeed the refutation, one would not need to deal with the other two at all.
1.e4 Nc6 2.d4 d5 3.Nc3
For a long time (in the analogous age of opening theory) this move order was considered a refutation of the Nimzowitsch Defence, and even today there are many players who do not touch The Dark Knight System against 1. e4 because of this very play. However, there is certainly no reason to do so. On the one hand, Black – if he is willing to take risks and at the same time seize the opportunities that present themselves – can calmly accept the critical play presented in the following, but on the other hand he can also evade it purposefully and without disadvantage.
The critical play with complications on both sides occurs after 3 … dxe4 4. d5 Se5. Without going into the jungle of variations in detail here, one can see that White is better developed (both bishops can get out of the game with attacks – Bb5 and Bf4, the Nc3 is aiming at b5, a possible figure attack over b5 can be supported by the queen via d4 etc.). The dark knight on e5 is more than wobbly (and will not stay there for long). And yet: White has yet to take back the pawn e4 (or play a real gambit with f3), and against the pawn d5, Black will attack with e6 and c6. It is perfectly possible to play it this way, especially if you want to play with Black to win – but you don’t have to. The alternatives are 3. … e6 and above all 3. dxe4 5. d5 Nb8.
I recommend the reverse order: First play the variant 4 … Nb8 (GM Rainer Knaak calls it “retreat – for equalization”) until you have developed a good and secure feeling for the position. Then you have a repertoire option, which you can use to retreat, especially against tactically stronger opponents. The chances of winning in this option are lower for Black, but so is the risk of loss – one could say extended “draw width”. Knaak even comes to the conclusion that white has no advantage whatsoever after 4… Nb8, which therefore also applies to the alleged refutation of 3. Nc3.
IM Andrew Martin, on the other hand, recommends changing to an original French with e6 already in the third move (with French-untypical adjustment of the black c-pawn). You should try this as soon as you have a secure repertoire foundation with the “retreat variant” Nb8 – or you can skip this option and go straight to the tactical Wild West game in the (former) main variant 3 … dxe4 4. d5 Ne5 .
1.e4 Nc6 2.d4 d5 3.exd5 Qxd5
With the pawn exchange on d5, White resolves the tension in the centre early and hopes to gain a development advantage by attacking the black queen. However, the black queen is not at all bad on d5.
If black “only” aims to equalize, 4.Nf3 e5 5.Nc3 Bb4 is a promising continuation.
More varied, but also more risky is the variation 4.Nf3 Bg4 with chances for both sides.
1.e4 Nc6 2.d4 d5 3.e5
The advance variation is the most important one in practice, probably also because the advance of the e-pawn is especially obvious when one does not know the other two options and does not want to calculate on the board. Moreover, it looks a little like the advance variation of the French (1. e4 e6 2. d4 d5 3. e5), although here Black has blocked his c-pawn (the typical French lever after c7-c5 cannot be realised so quickly).
But Black has other possibilities: the second French lever f7-f6 is still possible, and above all, the bad French bishop on c8 is not bad here at all, because it is not yet locked up. And to make sure that this doesn’t happen, it is developed quickly after f5 – and somehow this looks more like a better than a worse French.
As a result, in my experience, black only gets problems if white pins the dark knight with Bb5 and after short castling risks the black attack on the kingside, in order to proceed against the black king (standing in long castling) even on the queenside. A typical attacking game with opposite castles is created.