Beat The ... Philidor

IN this series I am looking at the statistically best way to play against popular opening lines.

The numbers are drawn from the 2021 edition of ChessBase's Mega database, ignoring, where possible, those results that include very few games and so are statistically insignificant.

The Philidor: 1.e4 e5 2.Nf3 d6 is a popular defence at club level, not least because it sidetracks both the Spanish and the Italian openings.

White's most-successful response is also the most-popular, namely 3.d4.

Position after 3.d4

Black has four main replies.

A) 3...exd4 (16,187 games)

White's best move, statistically, is the unusual but sharp 4.Bc4!?, which scores 66%.

Despite the looming threat to f7, Black has six replies that are popular enough to need looking at.

A1 4...Be7 is played almost half the time, the point being to develop the kingside while preventing a white piece landing on g5.

White does best by upping the sharpness with 5.c3!?, which scores 60%, after which the line splits again.

A1.1 5...Nf6 6.Qb3 0-0 7.Ng5!? scores 79% for White, although my main analysis engines Stockfish13 and Komodo12.1.1 much prefer 7.cxd4.

A1.2 5...dxc3?! runs into 6.Qb3, which scores 82%.

A1.3 5...d3?! also runs into 6.Qb3, which scores 67%.

A2 4...Nc6 is a transposition to a relatively minor line of the Scotch Gambit that normally arises from the move-order 1.e4 e5 2.Nf3 Nc6 3.d4 exd4 4.Bc4 d6!?

White scores 64% with both Nd4 and c3. The latter is much less common and complements A1, so I will go with it. After 5.c3!?, there is another split.

A2.1 5...Ne5 6.Nxe5 dxe5 7.Qb3 scores 64% for White.

A2.2 5...dxc3 6.0-0 scores 61% for White after 6...Nf6, 63% after 6...Be7 and 64% after 6...Be6.

A2.3 5...Nf6 6.Qb3 scores 76% for White.

A2.4 5...d3 6.0-0 scores 70% for White.

A2.5 5...Be6 6.Bxe5 fxe6 7.Qb3 scores 82% for White.

A3 4...Bg4?! leaves the kingside undeveloped but is surprisingly popular.

White scores an incredible 85% with 5.c3, after which Black has tried many moves, but their scores, albeit from small samples, shows how difficult the Black position is, eg 5...Bxf3 (20%), 5...dxc3 (0%), 5...Nf6 (17%), etc.

A4 4...h6?! is the type of move to be expected from a tournament novice.

White scores 84% with the calm 5.0-0.

A5 4...Nf6!? is by no means as bad as it might at first appear.

After 5.Ng5, which scores 58% for White, Black has two reasonable possibilities.

A5.1 5...d5 6.exd5

White's score leaps to 70% when Black plays 6...Nxd5?! (White is already winning after 7.0-0, according to the engines), but a much-better try is 6...Bb4+ 7.c3 Qe7+. There are only seven games with this sub-line in Mega21, but the chances look even after the engines' 8.Qe2 Qxe2+ 9.Kxe2 dxc3 10.Nxc3 (only one game, between a 2217 as White and a 2276 as Black, reaches this position in Mega21, and it was quickly drawn, but both sides can play on with reasonable chances of creating interesting play).

A5.2 5...Be6

White scores 80%, albeit from a small sample size, by taking the bishop-pair with 6.Nxe6.

A6 4...Be6 5.Bxe6 fxe6 6.Nxd4 reaches a position that more-commonly arises from the move-order 1.e4 e5 2.Nf3 d6 3.Bc4 Be6 4.Bxe6 fxe6 5.d4 exd4 6.Nxd4.

Black has four fairly popular replies.

A6.1 6...Qd7 7.Qh5+ g6 8.Qh3 e5 9.Ne6 scores 81% for White.

A6.2 6...e5 7.Ne6 scores 77% for White.

A6.3 6...Nf6 7.Bg5 scores 88% for White (from a very small sample size).

A6.4 6...Qf6 7.0-0 also scores 88% for White, but again from very few games).

B) 3...Nd7 (4,965 games)

Again White does best statistically with 4.Bc4, which again scores 66%, and here it is the most-popular move in the position.

Black has three popular replies.

B1 4...c6

White does best, 69%, with the slightly unusual 5.c3!?, when the line again splits.

B1.1 5...b5!? 6.Bb3 Be7 7.0-0 scores 64% for White.

B1.2 5...Be7? (second-most popular with 49 games, but it is a mistake) 6.Qb3 d5 7.exd5 scores 83% for White.

B2 4...Be7?

Again an early ...Be7 in the 3...Nd7 variation is a mistake. After 5.dxe5 Black has two popular replies, but 5...Nxe5 6.Nxe5 dxe5 7.Qh5 g6 8.Qxe5 scores 85% for White while 5...dxe5? 6.Qd5 scores 94% for White.

B3 4...h6!?

This is more respectable here than in A4, but White scores 79% by getting on with development with 5.0-0.

C) 3...Nf6 (4,717 games)

White scores 64% with 4.dxe5.

Black's idea is to restore material equality with 4...Nxe4, but 5.Qd5 Nc5 6.Bg5 scores 69% for White, rising to 73% after 6...Be7 7.exd6 Qxd6 8.Nc3 and dipping only marginally to 68% after 6...Qd7 7.exd6 Bxd6 8.Nc3.

D) 3...Bg4 (1,577 games)

White scores 79% with Paul Morphy's famous Opera Game reply 4.dxe5, rising to 86% after 4...Bxf3 5.Qxf3 dxe5 6.Bc4 and 86% after the gambit-line 4...Nd7!? 5.exd6 Bxd6 6.h3.