1.d4 Nf6 2.c4 e6 3.Nc3

Bb4 introduces the Nimzo-Indian Defence. Black develops their dark-squared bishop as actively as possible and pins the white knight. If not handled properly, this pin can cause problems for White for several reasons. The most positionally significant of these is that the pin nullifies White's control of the e4 square. White would like to play e4 at some point, but Black's knight on f6 dominates the square for now, since the c3 knight cannot recapture when pinned. Consequently, Black may be able to install their knight on e4 or otherwise use the square for his own purposes if White does not fight for it.

A second implication of the pin is that Black is threatening to exchange bishop for knight and double White's pawns. The resulting position would be unbalanced, with White trying to open the position to utilize the power of his two bishops, and Black working to keep the position closed and exploit White's pawn weaknesses. White must decide how they feel about this prospect when choosing their next moves.The Nimzo Indian defence is quite popular and there are a number of systems available to each side. White's fourth move options are listed below. Note that perhaps the most obvious move, 4. Bd2, breaking the pin and eliminating Black's threat to double White's pawns, is not among them. This is not because 4. Bd2 loses immediately; it does not. However, it is rarely seen in top level chess because it is far less ambitious than White's other choices.

The Classical Variation, 4.Qc2, aims to address two main problems posed by the Nimzo-Indian defence. On c2 the white queen protects the knight on c3, meaning that Black will no longer be able to double White's pawns by exchanging bishop for knight. At the same time, the queen hits the important e4 square.

A note on strategy and rules of thumb: Beginning chess players are often told not to move the queen too early in the opening. While as a general rule this advice is valuable, it is not sacrosanct. The Classical Nimzo provides an excellent opportunity to examine this rule, and its limitations, more closely. The admonition against early queen moves stems partly from the fact that the opposing player may be able to harass the queen simply by making useful developing moves. While one player is struggling to return his queen to safety, the second is gaining a decisive lead in development. In the Classical Variation, however, the queen's deployment to c2 is hardly a brazen sortie into enemy territory. It is unlikely that Black will be able to easily attack the queen anytime soon, so White's move is not considered risky.

A second reason to delay the queen's development is that the queen does not work well without the assistance of the minor pieces, and it is not clear until the knights and bishops are deployed where the queen will be most useful. With 4.Qc2, it is true that White neglects to develop a kingside piece or even to open lines for development, but it is clear that the queen will perform a useful function on c2. The fight for the e4 square is always a significant theme in Nimzo-Indian games, and the queen contributes to this fight. She also bolsters White's position on the queenside by protecting the pawn structure, and at the same time she takes aim at Black's kingside. White should not have a problem deploying the queen from c2 to whatever theater of battle requires her services.

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