While preparing the next game in Capablanca's games 'to be studied', which is Nimzowitsch - Capablanca, St.Petersburg 1914, I learned something new about the opening. It starts with the position shown in the diagram.
I usually open 1.e4, and sometimes answer 1.e4 with 1...e5, so I have played the diagrammed position countless times. What could I possibly learn about it, which arises after the further moves 2.Nf3 Nc6? Nimzowitsch - Capablanca continued 3.Nc3 Nf6 4.Bb5 (ECO C48-49) 4...d6. For some reason, I had never considered Black's fourth move. As Black, I usually play 4...Bb4 (C49), and I once analyzed 4...Nd4 (C48, the Rubinstein Variation) with Dr. Joseph Platz, my first and only chess teacher.
Why hadn't I ever considered 4...d6? Was it because of some Tarrasch dictum warning against shutting in the King's Bishop voluntarily with ...d6? Whatever the reason, if it was good enough for Capablanca, it is certainly good enough for me. I decided to investigate further.
I found the game in Kasparov's 'My Great Predecessors, Vol.1' as no.81, where he assigned the opening to ECO C62. Now I was really confused. I thought the opening was a Four Knights Game, but the 13th World Champion said it was a Ruy Lopez. The Capablanca game continued 5.d4 Bd7 6.Bxc6. Here Kasparov noted, '6.O-O exd4 7.Nxd4 Be7 leads to a tabiya of the variation, for example' 8.Re1, 8.b3, and 8.Nf5?!.
I checked my old copy of ECO and found under C62 (written by Keres) 3.Bb5 d6 4.d4 Bd7 5.Nc3 exd4 6.Nxd4 Nf6 and now ECO gave only 7.Bxc6. To reach the Kasparov tabiya 7.O-O Be7, is required. After 5...Nf6, ECO gave only 6.Bxc6!, with a note that 6.O-O is C66, the Berlin Defense to the Ruy Lopez, 3...Nf6.
Under C66 (also written by Keres) I found 3.Bb5 Nf6 4.O-O d6 5.d4 Bd7 6.Nc3, and now 6...exd4 7.Nxd4 Be7 is Kasparov's tabiya. Incidentally, if 6...Be7 7.Re1, then 7...exd4 is best. The move 7...O-O? is an old trap: 8.Bxc6 Bxc6 9.dxe5 dxe5 10.Qxd8 Rfxd8 11.Nxe5 Bxe4 12.Nxe4 Nxe4 13.Nd3 f5 14.f3 Bc5+ 15.Kf1 +-, as documented by Tarrasch.
Did Kasparov classify the opening as C62 erroneously? Perhaps. In any case, I had learned something new about an opening I had played many times.