Chess Opening Theory/1. d4/1...Nf6/2. c4/2...g6/3. Nc3/3...Bg7/4. e4

= King's Indian Defence =

4. e4
With 4.e4, White takes the King's Indian head-on, accepting the centre that black has conceded. Resulting games tend to be highly dynamic. Another important aspect of the move e4 is that it prevents black from playing 4...d5.

Theory table
.

'''1. d4 Nf6 2. c4 g6 3. Nc3 Bg7 4. e4'''