Philidor Defense (1. e4 e5 2. Nf3 d6)
I've been catching a lot of games where black tries the old line 3... Bg4. Isn't it amazing that although that variation has been proven obsolete so long ago with Morphy and the like that people still play it? The move 3... Bg4 is both unprovoked and ill-sighted because it violates some common opening guidelines.
A) Develop the knights before bishops... that is unless you play those open games like 1. e4 e5 2. Bc4 or 1. d4 d5 2. c4 Nf6 3. Bg5... because the knights tend to control the center better than bishops, and the bishops can wait to find better squares rather than rushing out there. Again it's a guideline, not a rule or law.
B) Moving a piece twice in the opening is usually a bad idea, where 3... Bg4 must move again after 4. dxe5, usually playing ...Bxf3 in the next two moves. But, again there are many openings where you move the same piece twice. The Ruy Lopez, Alekhine's Defense, Sicilian, and Scandinavian to name the main ones. But why is this bishop move so bad? It violates anothe guideline.
C) Don't develop undefended pieces. The bishop moves from c8 to g4 and is completely unprotected. Moves like Be7, Bd6, Bd7, Be6 are "safe" moves because the bishops are naturally protected by pawns and knights. But, you see these moves in all openings... Ruy Lopez again, Alekhine again, Sicilian again, and Scandinavian again... SO what's the issue with 3... Bg4 in the Philidor?
I believe the problem is not unique to the Philidor defense, because an early ...Bg4 may not be the best idea in a lot of openings... like the King's Indian defenses or even Scandinavian. After 1. e4 d6 2. Nf3 Bg4, black scores a measily 18%, whereas 2... c5 and Nf6 score into the 30%. After 1. e4 d5 2. exd5 Qxd5 3. Nf3 Bg4 black scores again under 20%, where other moves like 3... Nf6 and Nc6 score into high 20%.
Now why is this bishop move so bad for black? It isn't the same for the dark squared bishop... After 1. e4 e5 2. Nc3 Bb4 black scores a nice 27%; after 1. c4 e5 2. Nc3 Bb4 black scores a 37%! And after 1. e4 e6 2. d4 d5 3. Nc3 Bb4 black scores 27%. So there must be something intrinsically wrong with developing the queen's bishop early. It must have something to do with the kingside being undeveloped, whereas the queenside can usually wait a move or two.
Is it that simple? The mainline of the Philidor goes as follows:
1. e4 e5 2. Nf3 d6 3. d4 exd4 4. Nxd4 Nd6 5. Nc3 Be7 6. Be2 0-0 7. 0-0 Re8 8. f4 Bf8 9. Bf3 c5 10. Nb3 Nc6 11. Re1 a5, and the light squard bishop has yet to develop! This occurs in defenses like the French where the bishop stays on c8 for many moves, but why in the Philidor if it has such great access to the c8-h3 diagonal? Perhaps holding on c8 and just keeping watch of the diagonal is the purpose of the bishop as moves like an early ...Be6 in the Philidor can be drawish in a few matches or 9... Bd7 lost in its only game; 7... Bd7 scored only 1/5 games, and 6... Bd7 was a loss; 5... Bd7 managed .5/5; 4... Bd7 lost all 3 games; 3... Bd7 was a loss; and we know now that 3... Bg4 won 12 games out of 50.
So there is definitely something wrong with an early lightsquard bishop move in the Philidor. But that's the magic about it. As it sits on c8 for most of the opening it can guard the c8-h3 diagonal while maintaining the option of playing to a6 or b7 after some pawn moves, where it can really assert some pressure on the center. I'm not sure if this was what Philidor had in mind when he promoted 2... d6, did he know then that the c8 bishop should wait? Did he learn that by trial and error or was there something intrinsically wrong with developing that particular bishop early. A lot of questions... but what do you think? Does this occur elsewhere?