1.e4 c5 2.Nf3 Nc6 3.Bb5 Not a common move in the 1960s. In fact in Chess Sutton Coldfield's translation of Pachman's Semi-Open Chess published in 1970 the move is classified simply as "irregular". Nowdays, the move is named after GM Rossolimo and is very popular indeed being played by many of the World's elite. Rather than just a few lines the move has received a great deal of attention in several recent dedicated opening books.
3...g6 By far the most common reply. However, GM Kotronias prefers the straightforward 3...d6 not being concerned with the possibility of Bxc6 and a slight downgrading of Black's pawn structure. In contrast, another great expert on the Rossolimo-GM Bologan-thinks Black has difficulties after 3...d6 4. Bxc6. Yet another opinion is expressed by opening theorist Richard Palliser who considers Black's response of 3...e6 "deep and complex".
4.0-0 [4.Bxc6 is the other main line when Black may recapture with either pawn.]
4...Bg7 5.c3 A basic idea of the Rossolimo-domination of the centre by a rapid d4. White has another option here of the flexible 5. Re1 not yet revealing if Nc3 or c3 will be played.
5...Nf6 Choosing to counter-attack in the centre rather than an effort to restrain d4 with 5...e5. In the latter case ,though, White may still open the game immediately and play in gambit style with [5...e5 6.d4 as in, for instance, Vachier Lagrave-Naiditsch, EU-Ch Blitz Warsaw 2012 and Ivanov-Low, Washington 2006, with White winning both games.]
6.e5 The most direct move hitting the Nf6. White's other options here include guarding the pawn with 6. Qe2 or 6. Re1, and continuing in gambit style again with 6. d4.
6...Nd5 7.d4 cxd4 8.cxd4 0-0 9.Nc3 Nc7 This retreat leaves White with a space advantage although, as the position has features of an Alekhine Defence as well as a 2.c3 Sicilian, this is a playable option. Another different approach is [9...Nxc3 leaving White with a vulnerable c3 pawn when an early example continued 10.bxc3 d6 11.exd6 Qxd6 12.a4 Bf5 13.Ba3 Qc7 14.Re1 Bf6 Bronstein-Boleslavsky, URS-ch 24 Moscow 1957.]
10.Bf4 Securing the central pawn wedge at the cost of allowing Black to exchange the bishop on b5. [If White attempts to prevent this with 10.Ba4 then 10...d6 with the threat of Bg4 commences the process of dismantling White's centre.]
10...Nxb5 [10...d6 immediately is also feasible despite allowing White the chance to force some weak pawns onto Black-an example being 11.exd6 exd6 12.Bxc6 bxc6 13.Qa4 Qd7 14.Rac1 with level play as in Kovalevskaya-Rodionova, RUS-ch Higher League Kaliningrad 2015.]
11.Nxb5 a6 12.Nc3 d6 13.exd6 Bg4 This should generate enough play for the temporary offer of the d-pawn. On the other hand [13...exd6 leaves the d6 pawn slightly weak and White more space after 14.d5 ]
14.dxe7 The most principled move simply taking the offered pawn. However, possibly slightly stonger is [14.d5 Nd4 15.Qe1 Nxf3+ 16.gxf3 e5 17.dxe6 Bxe6 18.Qd2 when White's d-pawn looked strong in Quesada Perez-Filippov, Merida 2003.; Instead 14.h3 did not cause issues for Black after 14...Bxf3 15.Qxf3 exd6 (also possible was 15...Nxd4!? 16.Qxb7 e5 ) 16.Rad1 Izeta Txabarri-Azmaiparashvilli, Candas Open 1992.]
14...Qxe7 15.Re1 Qd7?! Although retaining an attack on the d4-pawn this move is not best. Black had a stronger way of doing this in [15...Qb4 with good play and a recent game continued 16.h3 (16.d5 now fails to 16...Qxf4 ) 16...Bxf3 17.Qxf3 Nxd4 18.Qe4 Qxb2 19.Rac1 Rac8 20.Nd5 Rxc1 21.Bxc1 Qxa2 22.Bg5-/+ as White had insufficient attack for the two pawns sacrificed in Belkhodja-Dourerassou, French T-ch Montpellier 2015.]
16.d5 Nd4 17.Be5 The most natural move in this position, attacking d4 with gain of time, and threatening to exchange off Black's powerful Bg7. Another way forward was the curious move [17.Re4 also gaining a tempo but using the d-pawn as a strong weapon eg 17...Nxf3+ 18.gxf3 Bh5 (18...Bf5 19.Re3 Rac8 20.d6 ) 19.d6 although in each case Black obtains some compensation for the pawn due to White's shattered kings-side]
17...Nxf3+ 18.gxf3 Bxe5?! A surprising error for such a good tactician as Hartston. After the exchange Black is left with weak dark squares around his king. Instead there is the hidden line [18...Rae8 which secures Black a decent game after either 19.fxg4 (as well as after 19.Bxg7 Rxe1+ 20.Qxe1 Bxf3 21.Qe5 (21.Bxf8 of course loses to 21...Qg4+ 22.Kf1 Qg2# ) 21...Qg4+ 22.Qg3 Kxg7 ) 19...Bxe5 ]
19.Rxe5 Bh5 [19...Bh3 is no better as White has an extra pawn as well as a big space advantages following 20.Qd4 After this move White's king remains safe and the queen's rook can occupy a central file in support of the d-pawn being pushed.]
20.Ne4 With an obvious but powerful threat to fork the Black king and queen.
20...Qh3 This looks quite threatening with the idea of Bxf3 and mate on g2. However, the overriding factor in this position is the weak black squares on the a1-h8 diagonal which White exploits in a very accurate manner. [If 20...f6 then 21.Re6 and Black cannot defend f6 eg 21...Kg7 22.Qd4 ]
21.Nf6+ Kh8 [21...Kg7 makes no diference. One possible line being 22.Qd4 Bxf3 23.Rg5 Kh6 24.Rg3 winning a piece whilst the Black king stays in grave danger.]
22.Qd4 Bxf3 [22...Rad8 loses quickly to 23.Nxh5 gxh5 24.Rxh5+ and the queen is lost.]
23.Rg5 Qh6 At least now, in certain lines, the discovered check can be blocked by Qg7 but White has an even stronger reply. [Also development with 23...Rac8 does not help Black since 24.Rg3 leaves Black in terminal difficulties 24...Qf5 and White has many ways to win the simplest being 25.Nd7+ (or just pushing the passed pawn with 25.d6 ) ]
24.Rg3 The bishop now has no good move so Black resigned. For after [24.Rg3 Bh5 25.Nxh5+ the bishop is lost and even Qg7 is not feasible.] 1-0