411 REFERENCE · Wikibooks
Chess Opening Theory/1. f4/1...e5/2. fxe5/2...d6/3. exd6/3...Bxd6/4. Nf3/4...g5
Reference material by Wikibooks contributors. This retains its source identity and is not 411 news reporting.
Bird's Opening rd nd bd qd kd nd rd pd pd pd pd pd bd pd nl pl pl pl pl pl pl pl rl nl bl ql kl bl rl
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.
Theory table
+56h3??
Bg3#0-1g3
g4Nh4 +/=
References