Defending the 2 knights attack by attacking
Black often does Bf5 in the Main line.
Black can do other moves, but Bf5 is the normal way of playing it.
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The 2 Knight Attack tries to counter the Bf5 line.
It sets a trap of sorts against it.
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So the lines are completely different
What line was you wanting to talk about exactly?
Bf5 Main line or 2 Knight Attack line