Ideas Behind The Jobava-Prié (part two)

HISTORICALLY, Black's first response to 1.d4 d5 2.Nc3 Nf6 3.Bf4 was 3...a6!?
The move occurred in James Mason - Max Weiss, Vienna 1882, and might cause a few sniggers.
But, as I mentioned in part one of this series, it has since been played by Carlsen, Caruana, Svidler and Nakamura, so should be taken seriously.
Black's obvious point is to prevent a white piece landing on b5. Black argues that a tempo spent on a passive move in this position is not important as White is not in a position to open/put-pressure-on the black centre with c4 or e4.
White usually replies 4.e3 rather than 4.Nf3. Both moves are useful and absolutely normal, but the former gives White the option of meeting 4...Bf5 with 5.f3!?.

Position after 5.f3

This plan occurred in the following game from the 2018 Korchnoi Memorial in St Petersburg.
Denis Pershin (2403) - Hannes Stefánsson (GM 2511)
5...h6!?
More popular is 5...e6, but the text is the choice of the analysis engine Komodo10, and the game soon transposes to better-known lines.
6.g4 Bh7 7.h4 e6 8.Bd3 Bxd3 9.Qxd3
The play is reminiscent of the main line in the Classical Caro-Kann, but with a less-open centre.
9...c5 10.Nge2 Nc6 11.Kf2?!
Most players have preferred 11.0-0-0.
11...Bd6 12.Na4?!
This decentralisation does not help White's cause.
Stockfish10 gives 12.Kg2 Rc8 13.Bxd6 Qxd6 14. Ng3, but prefers Black.
Komodo10 gives 12.dxc5 Bxc5 13.Nd4 0-0 14.Nxc6 bxc6 15.Bg3, again with an edge to Black.
12...cxd4 13.exd4 Bxf4 14.Nxf4 Qd6 15.Ne2 e5!?
Provoking an immediate crisis. The calmer 15...0-0 is not necessarily better after White replies 16.g5.
16.dxe5 Nxe5 17.Qd4
The engines reckon White had to find 17.Qa3!?, although Black must be better after 17...Qxa3 18.bxa3 Rc8.
17...Rc8
This simple move proves very difficult to meet.
18.Nec3
The engines reckon best is 18.g5 Nfg4+! 19.fxg4 Rc4 20.Qb6 Nxg4+ 21.Ke1 Qe5 22.Nac3 0-0 23.Rd1 Ne3, but with a winning attack for Black.
18...Nfxg4+! 19.Kg2
Or 19.fxg4 Qf6+ 20.Kg2 Qf3+ 21.Kg1 Qg3+ 22.Kf1 Rc4 23.Qg1 Qf3+ 24.Ke1 0-0, when White will not survive long.
19...Rc4 20.Qb6 Rc6 21.Qd4 0-0 22.Rae1
Or 22.fxg4 Rc4 23.Qf2 Rxg4+ with a winning attack.
22...Rc4 23.Qb6 Qd7 24.b3 Rf4 25.Rh3 d4 26.Nd1 Rc8 27.Re2 Nxf3!? 28.Rxf3 Qd5 0-1
In the final position, White is getting mated. Note how the black knight at g4 was able to stay at its precarious-looking post for more than a third of the game.
White has a major alternative, after 4...Bf5, in 5.Bd3, seeking to swop off the well-placed black bishop. I will look at this plan in part three.