White defends the pawn
When one of your pawns is attacked, your natural reaction is to defend it.
This previous line usually appear after the Four Knights Opening is played. This is a common fork in many Chess positions. So Knight to c3 gives Black too much play here, thus the modest d3 is the best way to protect e4 here.
I want to mention that this is not the only opening where the modest d2-d3 is better than the seemingly active Nc3. You can find the same idea in the Berlin defense, although the underlying reasons are different.
Now Black usually develops his Bishop next. There are mainly two possible squares here: c5 (slightly more active) and e7 (slightly more solid).
Black Moves The Bishop To c5
This line is called the Giuoco Pianissimo and is tackled in another article. It can also arise from the Giuoco Piano is which Black plays 3… Bc5 immediately. It is a fascinating system, but in this page, I am focusing on the typical sharp lines arising in the Two Knights Defense.
Black Plays The Bishop To e7
But before getting there, we have to review the possible ways to follow up after White plays d2-d3, and there is one last interesting quiet line I want to share with you.
The game goes on and each side has its chances, but White can forget about the slow positional game he was probably intending to play (else, why play 4. d2-d3 ?). So even if the position remains balanced, this is probably a moral victory for Black to fight on his own terms.
This final position is very similar to a Marshall attack without the attack for Black ! So of course very bad for Black. Hence, after Re1, Black accepts to play d7-d6 and the quiet game everyone has been waiting for is finally here !
As already said, this is the start of an interesting maneuvering game in which White has a small edge and Black gets a solid position.
We have seen what happens when White defends the pawn with d2-d3. This line is very popular at top level because there is no straightforward way for Black to equalize quickly. Yet, usually, at club or intermediate level, another sharper move is usually chosen…
Two Knights Defense: White Attacks With 4. Ng5 !
White is not forced to defend the pawn but can also start pressuring the f7-pawn in a very convincing way ! Most of this article is dedicated to the very sharp 4. Ng5 attack from White !
Thus Knight to g5 is not a cheap tactical move, but a very serious threat ! (Also, on g5, the Knight defends e4 !).
Black defends With the Main Line
As we will see very shortly, Black does have a good defense after 4. Ng5.
d7-d5 was the only move for Black. We will now delve into one of the sharpest opening system: one inaccuracy and you’re (usually) lost ! It is White’s turn to find the right move !
The previous line should act as a reminder that applies in many lines of the Two Knights Defense: Don’t think positional, think tactical. And don’t rely on generic principles, calculate accurately !
This is (again !) an important moment. Anyway, in this opening, almost any move is a critical decision.
Why is the capture on d5 considered as a bad move for Black ? This deserves another section !
Black Captures On d5
As I told you, capturing on d5 is bad is considered weak.
The threat on g5 may look scary, but White has not one, but two excellent ways to deal with it !
With Black, you may be able to survive on perfect play, but let’s be honest, you won’t play perfectly so White will win this 9 times out of 10.
White’s other reply is supposed to be better in absolute strength, although it is far more complex: the tree of possible moves goes bigger from the beginning !
This previous line is very pleasant to play with White: a long term advantage without taking much risk. But Black does not necessarily cooperates and can try to muddle things up.
Imagine going into the last line without any idea of what you are playing with White: you are better but there are chances that Black can successfully outplay you.
So which line should you choose with White ? The straightforward, practical Nxf7, or the more ambitious, but also more difficult d4 ? A matter of taste, really, knowing that Black will not often capture on d5.
Knight To a5: The Main Line
For all the reasons developed in the previous section, Black usually prefers to move the Knight away, which is a much better choice !
Years of experience tell us that chances are about equal here. However, the position is full of possibilities.
This line is probably the most played variation when the Two Knights Defense appears. So you won’t waste any time by studying it a little bit. It is sharp, unbalanced and interesting for both sides.
The Fritz And Ulvestad Variations of the Two Knights Defense
The previous line is certainly the line Black chooses to follow 90% of the time in the two Knights defense, and rightly so: this is a perfectly sound line.
However, Black may also try to destabilize his opponent by playing a sideline. The Fritz and Ulvestad variations are somewhat connected as they can result in exactly the same position. They are probably not as sound as the main line, but are complex enough to surprise White and emerge with an interesting position. Both lines start after White has played 5. exd5.
Let’s now check another possible move by Black: the Ulvestad variation.
You can see that all those lines are coming down to a similar result: a position in which White is usually one pawn up, but not a great development, and where Black has better attacking chances. But according to the line chosen, this can favor White or Black, or none of them ! The last example clearly favored White.
As 6… Qxd5 is not a good move for Black, the best option for Black is to move the Knight away and come back to the Fritz variation.
To conclude on those two variations, Black gets practical chances if he sticks to the moves, but any suboptimal move can be deadly ! On best play, this should be slightly better for White, but the position is so complex that it should not matter that much.
Black Ignores The Attack In The Two Knights Defense: The Traxler
We started studying the lines with 4. Ng5 mentioning that Black must defend the f7 pawn. What a narrow-minded mindset ! What if, instead, we try to build an even bigger attack ? This assumption is the basis of the Traxler variation (also known as the Wilkes-Barre).
White Captures On f7 With The Knight
But again, the position is so complex anyway that you can get a winning or losing position in one move. This is typically a position where your fighting spirit matters a lot !
White Captures On f7 With The Bishop
The previous lines, very sharp and tactical, might not be your cup of tea, or maybe you have just better to do with your life than spending one hour to study the tactical traps of the Traxler. Thus, for those looking for a simpler line to play, White can also capture with the Bishop on f7.
Capturing with the Bishop also gives some initiative to Black, but the lines are a lot less crazy than the ones starting with 6. Nxf7. The move order matters and there are more possible moves for each side. Thus we will review a few lines covering the main ideas for both sides: even if your game does not follow exactly one of those lines, you will be able to reuse the ideas anyway !
Let’s be clear: there are very few chances that you find yourself playing this line, but this typically shows how Black’s slight disadvantage in the Traxler can turn into a commanding position for Black !
This is enough for an overview of the Traxler: a dangerous line… for both players ! But if we are completely honest, it should give White a significant advantage on best play. That leaves some room for experimentation though !
White Plays 4. d4
Instead of defending e4 and instead of going after the f7-pawn with Ng5, White has this third possibility.
This last move d7-d5 is a pattern to remember when White has pushed e4-e5 with a Bishop on c4: this is often the only move that keeps the balance for Black in tense situations like this !
Conclusion on the Two Knights Defense
You are now familiar with the main lines of the Two Knights Defense, and you know enough of the dynamics to be able to navigate through this opening. You know enough to start playing it and check in which lines you feel the most comfortable.
This opening is one of the sharpest you can find and it is tactically very demanding. If you like that kind of positions, you should always play opening systems that suit your style. Outside the world of open games, the Semi-Slav and some Sicilian defenses come to mind. Be sure to check the underlying ideas before playing them !