Chess Opening Theory/1. e4/1...d6/2. d4/2...Nf6/3. Nc3/3...Nbd7

A sideline in the Pirc defence, where Black wants to play ...e5. Playing ...Nd7 first increases Black's control of e5 by unpinning the d6 pawn from the queen: whereas if 3...e5, White had the option of a favourable queen trade (dxe5 dxe5 Qxd8+ Kxd8), 3...Nd7 obstructs the d-file and so threatens 4...e5.

The Lion defence is essentially a move order trick. The resulting structure, with pawns on e5 and d6, is the same as the Philidor defence (1. e4 e5 2. Nf3 d6). However, if Black attempts to develop in the same way (with ...Nd7 and ...Nf6) in the conventional Philidor move order,

• After 3. d4 Nd7 (the Hanham variation), instead of 4. Nc3 White can play 4. Bc4!, and 4...Ngf6? loses tactically. 5. dxe5 Nxe5 6. Nxe5 dxe5 7. Bxf7+ Ke7 (7...Kxf7 8. Qxd8 Bb4+ 9. Qd2 Bxd2+ 10. Nxd2±) 8. Qxd8+ Kxd8± White goes into an endgame up a pawn.
• After 3. d4 Nf6 (the Nimzowitsch variation), White has the critical move 4. dxe5, where 4...dxe5? 5. Qxd8+ Kxd8 6. Nxe5± and White goes into an endgame up a pawn.

In this move order, after 1. e4 d6 2. d4 Nf6 the e4 pawn is en prise so 3. Nc3 is compelled, and Black can reach a Philidor defence where White has played a less critical line.

4. Nf3, developing a piece, is the most common move but allows 4...e5: Black takes some central space at last and is happy to allow 5. dxe5 dxe5.

4. f4, the Anti-Philidor, is the most critical move. It increases White's control of e5. After 4...e5 the main line is 5. Nf3 and Black is compelled to capture 5...exd4, otherwise 5...Be7? 6. fxe5! dxe5 7. dxe5 wins a pawn.

The system was popularised by Dutch chess amateurs Jerry van Rekom and Leo Jansen, who coined the name for this move order in their 2009 book on the system, The Black Lion.^[1] A contemporary review characterised the two Dutch amateurs as "very positive about their system [but] their enthusiasm tends to lead to subjectiveness", concluding "The big advantage of the Black Lion for club players is clearly that many White players will overestimate their chances."^[2]

In 2022 Grandmaster Simon Williams revisited the opening in his Chessable course and accompanying book, where he pitched it as an aggressive surprise weapon.^[3]

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