Chess Opening Theory/1. e4/1...e5/2. Nf3/2...Nc6/3. Bb5/3...f5

Jaenisch gambit
	a b c d e f g h 8 7 6 5 4 3 2 1 8 7 6 5 4 3 2 1 a b c d e f g h
	Position in Forsyth-Edwards Notation (FEN) r1bqkbnr/pppp2pp/2n5/1B2pp2/4P3/5N2/PPPP1PPP/RNBQK2R
	Moves: 1. e4 e5 2. Nf3 Nc6 3. Bb5 f5
	ECO code: C63
	Parent: Spanish game
	Synonym(s): Schliemann defence
	Responses: ; 4. Nc3 · Dyckhoff variation; 4. d3;

3...f5 · Jaenisch gambit

The first thing to know about the the Jaenisch gambit, aka the Schliemann defence, is that it is not a gambit. Despite the apparent similarity to the Latvian gambit, Black's knight on c6 changes everything.

Capture a pawn ?

Unlike in the Latvian, White can't capture on e5 immediately, and capturing on e5 after exchanging on c6 (4. Bxc6 dxc6 5. Nxe5) doesn't win the pawn either because ...dxc6 let Black's queen into the game, and the usual Ruy López rejoinder 5...Qd4! wins it straight back. Ah, thinks White, don't I have the intermezzo 6. Qh5+, with the knight controlling g6? Unfortunately this falls into a common trap. 6. Qh5+?? g6 7. Nxg6 hxg6 and the rook is defended by Black's queen.

The pawn on f5 isn't free either. 4. exf5?! and 4...e4 embarrasses the knight, who (again, because of that knight on c6) doesn't have the e5 or d4 squares to move to. After 5. Qe2 Qe7 6. Bxc6 dxc6 7. Nd4, the game may even end in a draw by repetition after 7...Qe5 8. Nf3 Qe7 etc.

So rather than blast the Jaenisch off the board, White must act natural and wait to exploit Black's weakened kingside further down the line.

Defend e4

Black's pawn on f5 is threatening ...fxe4, so White should choose a move that helps to defend e4. The choice is 4. Nc3 or 4. d3: would White prefer to recapture with a knight or a pawn?

4. Nc3 is the Dyckhoff variation. Recapturing with the knight (4...fxe4 5. Nxe4) invites 5...d5, and leads to the hair-raising sacrifice 6. Nxe5! and a razor-sharp repudiation of the gambit.

4. d3 is a popular and less sharp alternative, intending to recapture on e4 with the pawn. After 4...fxe4 5. dxe4 Nf6 the pawn does not need to be defended directly because after 6. O-O Nxe4? White can recover it tactically with Re1.

Counterattack e5

4. d4!?, the Schönemann attack, allows 4...fxe4, intending 5. Bxc6 dxc6 6. Nxe5 ⩲.

History

3...f5 was analysed by Carl Jaenisch in Le Palamède in 1847. He analysed 4. d4, 4. exf5, and 4. Bxc6, concluding, "Seems likely to be a good defence for Black."^[1]

von der Lasa's Handbuch des Schachspiels associated the line with Adolf Schliemann and gave the appraisal, "If White accepts it or declines it with 4. d4, Black appears to achieve at least an equal game; conversely, White seems to gain a slight advantage with 4. d3 or 4. 0-0. However, precise analyses of this are still lacking."^[2]

Theory table

1. e4 e5 2. Nf3 Nc6 3. Bb5 f5

	4	5	6	7	8	9	10	11	12	13
Dyckhoff variation	Nc3 fxe4	Nxe4 d5	Nxe5 dxe4	Nxc6 Qg5	Qe2 Nf6	f4 Qxf4	Ne5+ c6	d4 Qh4+	g3 Qh3	Bc4 Be6	⩲
Tartakower variation	... ...	... Nf6	Nxf6+ Qxf6	Qe2 Be7	Bxc6 bxc6	Nxe5					⩲
	d3 fxe4	dxe4 Nf6	O-O d6	Nc3							⩲
Schönemann attack	d4 fxe4	Bxc6 dxc6	Nxe5
Jaenisch gambit accepted	exf5 e4	Qe2 Qe7	Bxc6 dxc6	Nd4							=

References

↑ "ce qu'elle nous paraît susceptible d'une bonne défense pour les Noirs." de Jaénisch, C.-F. "Le Début Royal Ch. IV". La Palamède (in French): 538–542.
↑ "Das Gegengambit wurde von dem verstorbenen Dr. Schliemann empfohlen. Nimmt Weiß es an oder lehnt er es mit 4. d4 ab, so scheint Schwarz ein mindestens gleiches Spiel zu erlangen; dagegen scheint Weiß mit 4. d3 oder 4. 0—0 etwas in Vorteil zu kommen. Genaue Analysen hierüber fehlen jedoch noch." von der Lasa, P. R. (1891). Handbuch des Schachspiels (in German) (7th ed.). Leipzig: Verlag Von Veit & Comp. p. 223.

Jaenisch gambit
a b c d e f g h 8 7 6 5 4 3 2 1 8 7 6 5 4 3 2 1 a b c d e f g h
Position in Forsyth-Edwards Notation (FEN) r1bqkbnr/pppp2pp/2n5/1B2pp2/4P3/5N2/PPPP1PPP/RNBQK2R
Moves: 1. e4 e5 2. Nf3 Nc6 3. Bb5 f5
ECO code: C63
Parent: Spanish game
Synonym(s): Schliemann defence
Responses: 4. Nc3 · Dyckhoff variation 4. d3