1...Nd6 2.Bd3 Bd7 was a safer choice.

3...cxd5?! 4.Bxf6 gxf6 5.Rge1+ Kf8 6.Qc3 etc.

Creating a powerful protected passed pawn.

6...Qa5 was correct. although after 7.Rd4 , preparing b2-b4, White keeps the advantage.

With the double threat of 9 Nd4 and 9 Rxa7. White is practically winning.

Removing the queen from the vulnerable d-file before White puts a rook on d1, and taking the g4-square away from his queen.

Gaining some space and preparing a future pawn storm on the queenside.

White has just a slight edge – Korchnoi.

A "mysterious" rook move, realizing that Black's only viable plan is ...b6-b5.