Just in time! White will be the owner of all the light squares (f5, d5, c4) and is looking at a scenario where the knight is much better than the bishop.

The position is around equal, but can you find a plan to take advantage of a weak square?

We have seen this maneuver in another one of Botvinnik's games. He wants to support a knight jump to c6 in the future. In case Black trades on b4, White would win another tasty square on b4 for a knight.

Petrosian kicks the knight on e5 but on the other hand, his bishop on g7 will be restricted and some weakness will be created as well.

Nb4-Nc6 or Bc3-Bb4 are some interesting plans here for White.

4...Bf7! was better!

Bb4 is the threat winning a piece.

Bb4 is coming and d5 will suffer.