1.c4
e5
2.Nc3
Nc6
3.Nf3
Nf6
4.g3
Bb4
5.Bg2
This line has a completely different character compared with the previous one. White doesn't avoid the exchange on c3, relying on the force of the pair of Bishops and hoping to prove that, in a certain way, he would improve his structure in the center. After
5...0-0
6.0-0
Black's main choice is
6...e4
We shall examine it first and only then, by comparison, the alternatives 6...Re8, 6...Bxc3 and 6...d6.
A few decades ago, one of the most popular accolades was the position arising after
7.Ne1
Bxc3
8.dxc3
h6
9.Nc2
Re8
10.Ne3
Black has considerably reduced the elasticity of the white Pawn Structure and enjoys stability for his Knights. On his part, White hopes to take advantage of the central dark squares, weakened by the advance of the black central Pawn. His knight is perfectly placed on e3: blocking the Pawn, preventing Ff5 and controlling d5. The pair of Bishops could also count at some moment.
In order to fight for an advantage, White has two main plans: to play Nd5 at the right moment and f2-f4 in order to win space on the other wing and open the diagonal of the other Bishop in case of exf3, exf3. If Black would not take en passant, White would have chances for a positional attack on the king side. It can also happen the other way; as already stated by Nimzovich, an unpromoted Pawn formation can become the object of an attack.
Black would try to maintain the position closed and if possible, to exchange the light squared Bishops. In this latter case, not only the White King position would be seriously weakened, but also a whole complex of squares in White's camp. Besides, without his colleague around , the dark squared Bishop would become a potentially bad piece. Also favorable for Black would be the exchange of one pair of Knights, only not on the d5 square; for instance, by means of Nc6-e5-g4.
At the preparatory moves from the next phase of the game have to be regarded from the perspective of the just mentioned long term plans. Sometimes, the sensation is that both sides are playing a waiting game, watching each other's intentions. Whenever this type of play was seen in a game at the highest level the observers commented that both opponents decided to take a day off, by making a fightless draw after the exhausting previous game. This position has much more life in it than it was traditionally considered.
After the most common
10...d6
White usually continues with
11.Qc2
putting some additional pressure on Pe4, in order to restrict Black's possibilities. Although there seems to be no direct threat, Black should be careful in order to prevent the pressure to become too strong.
What is the possible continuations.
11...Re5 might seem a bit eccentric, but has some concrete plan behind it.
11...Bd7 is a natural developing move but leaves White with sufficient liberty of action in order to maintain the initiative.
11...Ne5 is an interesting Pawn sacrifice: Black ignores the intention of c2, to put pressure on the central Pawn. Accepting the sacrifice seems to give White very few chances for an advantage. Black can either play a Pawn down with opposite color Bishops or fight against the pair of Bishops in conditions of material equality.
11..a5 is quite popular. Black makes an useful move, waiting for White's intentions in order to define his own plans. This leaves White just as
11...Bd7, with too much freedom of action.