Fianchetto Variation, Nimzowitsch Variation, Quiet Line

The Quiet Line, 5. b3, is the most common reply to 4...Ba6. White defends c4 with a pawn rather than the queen or knight, and in exchange loosens the c3 square and the long diagonal. Black most often answers at once with 5...Bb4+, the Check Variation, which aims at the weakened c3 square. Less common are 5...d5, striking at c4, after which White scores well, and 5...Bb7, which returns the bishop to the long diagonal. The engine rates the position as roughly balanced.