These first four moves can be played against virtually any Black responses. During these first four moves, White has not revealed how he will attack. While Black have most likely committed to a specific defense. White’s attacking lines include: the English c2-c4, the Catalan d2-d4, the King’s Indian Attack d2-d3 followed by an eventual e2-e4. If Black plays an immediate d7-d5, White can, if he chooses, immediately interject c2-c4 for the Reti (1.Nf3 d5 2.c4) or d2-d4 for the Catalan (1.Nf3 d5 2.d4 Nf6 3.c4 e6 4.g3) .
The Barcza System is often used by White as way to direct the game into the King’s Indian Attack. Here are some examples: