411 REFERENCE · Wikibooks
Chess Opening Theory/1. e4/1...e5/2. Nf3/2...Nc6/3. Bc4/3...Nf6/4. Ng5/4...Nd5
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Two Knights Defence rd bd qd kd bd rd pd pd pd pd pd pd pd nd nd pd nl bl pl pl pl pl pl pl pl pl rl nl bl ql kl rl 1. e4 e5 2. Nf3 Nc6 3. Nc4 Nf6 4. Ng5 Nd5 C57-C59 Italian Game
Two Knights Defence
4...Nd5?
Rather than blocking with the pawn, black elects to use the knight. This opens a discovered attack on the white knight as well.
White should not agree to trade knights with exd5 or Bxd5. This will give Black counterplay with their queen on g5 and force White to castle, completely losing their attack on Black's f-pawn.
Theory table
1.e4 e5 2.Nf3 Nc6 3.Bc4 Nf6 4.Ng5 Nd5
5
1
d4h6
+/=
2Nxf7Kxf7+/=
References
Two Knights Defence