Chess Opening Theory/1. e4/1...e5/2. Nf3/2...Nc6/3. Bb5/3...f5/4. Nc3/4...fxe4/5. Nxe4/5...Nf6/6. Qe2/6...d5/7. Nxf6/7...gxf6

8. d4, threatening the e5-pawn, is the move that really gets to grips with Black's pawn centre - given that 8.Nxe5 straight away is not possible because the White queen is pinned after 8...fxe5 9.Qxe5+ Qe7.

Krum Georgiev tried 8. Nd4, not to show off how many Black pieces White has managed to pin, but to threaten a queen check on h5 that would deprive Black of castling rights. It's not such a threat though, as ...Qd6 solidifies the c6-knight and makes room for the king on d8.

An improved version of 8.Nd4 is 8. O-O, which was played three times in the 2014 world rapid and blitz championships in Dubai. White postpones the decision about what to put on d4. If Black pre-empts Nd4 with ...Qd6, White can switch tack with 9.d4.