This opening is also called Philidor’s Opening. It was examined in the Gottingen Manuscript, and by Lucena and Lopez but it was Philidor who mapped out the theoretical foundation in a true explorer’s sense. He saw the point of B-B4 (Bf1-c4) as striking immediately at the weakness of the f7 square in chess with dangerous plan P-KB4 (f2-f4).
The Germans developed a defense against it called the Berlin system that continues 2. …. N-KB3 (Nf6) which neutralizes P-KB4 (f2-f4) by 3. …. P-Q4 (d7-d5) that set the tone for value seen in a central counter-thrust for active counterattack in other opening positions.
White has ways to continue his aggressive posture after 1. P-K4 P-K4 2. B-B4 against various ideas seen by Black over the years. Lets take a look a some examples:
2. … B-K2 is a blunder because after 3. Q-R5 g6 4. Q:K5 N-KB3 5. P-Q3 leaves White a pawn up with good development.
Following suit by 2. … B-B4 (Bf8-c5) was a popular way for Black to play the defense. The volume of possible variations from this gives me an opportunity to recommend the excellent pamphlet book by 7th World Champion Yakov Estrin with Igor Glazkov titled 3 Double King Pawn Openings, featuring the Bishop’s Opening, Hungarian Defense and Ponziani Opening.
2. … P-QB3 3. P-Q4 P-Q4 (3…N-B3 4. P:P N:KP 5. Q-K2!) 4. P:P P:P 5. B-QN5+ B-Q2 6. B:B+ N:B 7. P:P N:P 8. N-K2 N-B3 9. O-O B-K2 10. N-QB3 with a pull.
A great investigative master was Bent Larsen and a brilliant player who explored and played many of the offbeat lines where he introduced favorable positions and sharp games in his own practice (namely, he walked his talk and writings.) So lets take a look at just one from his book Bent Larsen’s Best Games – Fighting Chess with the Great Dane.
White: Bent Larsen vs. Black: Bela Berger Bishop’s Opening 1964 Amsterdam Interzonal
1. e4 e5 2. Bc4 Nf6 3. d3 d5
Here, Larsen gives d5? stating that his opponent underestimated his modest opening system. This whole variation goes back many years with much analysis and Black’s handling of this position was commonly known as playable. What Larsen objectively gives as his own treatment of the position’s merits and subsequent play of this particular line illustrates Larsen’s superb positional and attacking judgment.
4. e:d5 N:d5 5. Nf3 Nc6 6. O-O Bg4
The game Ernst -Gerhard, Berlin 1935 continued: 6…Be7 7. R-e1 f6 8. d4 e:d 9. N:d4 N:d4 10. Q:d4 Nb6 11. Qe4 N:c4 12. Q:c4 c6 13. Nc3 Kf8 14. Bf4 and White is better.
7. Re1 Be7 8. h3 B:f3 9. Q:f3 Nd4!
Forces White to pull up some magic; example being 10. Q:d5 Q:d5 11. B:d5 N:c2 keeps Black in the game. After 10. Qd1, Black gets time to breathe.
10. Qg4! O-O 11. R:e5 Nf6 12. Qd1 Bd6 13. Re1 Re8 14. Be3
White is a pawn up and adds to his pluses.
14. … c5 15. Nd2 Bc7 16. Nf3 Qd6 17. B:d4 c:d4 18. R:e8+ R:e8 19. c3 d:c3 20. b:c3 Nh5?
Knight on the rim is not square minded. Better was a defensive Re7. White now increases square count. 21. Qa4! Re7 22. Q:a7 Nf4 23. Q:b7 h5 24. Qc8+ Kh7 25. h4 1-0).