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

= Schliemann Defence =

The first thing to note about the Schliemann Defence, formerly known as the Jaenisch Gambit, is that it isn't a gambit. Despite the apparent similarity to the Latvian Gambit, the knight on c6 changes everything. Obviously, White can't capture on e5 immediately, and capturing on e5 after exchanging on c6 doesn't win a pawn either because the usual Ruy Lopez rejoinder ...Qd4 wins it straight back. Capturing the other way with 4.exf5 is possible but then 4...e4 would embarrass the f3-knight and lead, surprisingly, to a draw by repetition after only 7 moves.

So rather than blast the Schliemann Defence off the board, White must try to act natural and exploit the weakened Black kingside further down the line. The two moves that contribute to White's development while also defending the e4-pawn are Black's next move is going to be ...fxe4, so choosing between these two moves amounts to choosing which piece you want to recapture with. A knight on e4 would immediately invite ...d5, to which White can react with a hair-raising temporary piece sacrifice. A pawn on e4 creates the prospect of preventing Black from castling with the remarkable manoeuvre Qd1-d3-c4. A little theory goes a long way in both cases!
 * 4. Nc3, the Berger Variation, and
 * 4. d3, the Safe Variation.

Theory table
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 * 1.e4 e5 2.Nf3 Nc6 3.Bb5 f5