This move defends the c6-knight and prepares the development of the kingside.
1. e2e4  1... c7c5  2. g1f3  2... e7e6  3. d2d4  3... c5d4  4. f3d4  4... b8c6  5. b1c3  5... a7a6 The most popular move is 5...Qc7, but my favorite has always been 5...a6. I've played this position so many times with Black that I've lost count. 6. c1f4 White has many different attempts here. This move is only the eighth most popular. 6... d7d6  7. f4g3  7... f8e7  8. f1e2 