Chess Opening Theory/1. f4/1...e5/2. fxe5/2...d6/3. exd6/3...Bxd6/4. Nf3/4...g5

4...g5
This is the Lasker variation, the most aggressive and double edged line. Black now threatens g4 followed by Qh4+, Bxg3+, and mate to follow. The most common move, and, according to Lakdawala, "Our only hope of wresting the advantage". The game now turns into a full-blown firefight.