Grob Opening starts with 1.g4. Its an aggressive opening for white that opens the kingside pawns and aim to developed the pieces quickly.
Like the Polish opening, this move also ignores the centre’s control. In addition, move 1.g4 weakens White’s kingside, where White is most probably going to castle. Therefore this is not very popular opening for white.
Black can choose his set-up here with either 1.d5 or 1.e5. But 1.d5 is the strongest move since it attacks the g4 pawn directly.
The Grob gambit
White often plays the Grob gambit with 2.Bg2, sacrificing the g4 pawn for development. The idea is to play 2…Bxg4 3.c4 attacking the center immediately.
It is interesting that black can take on c4 here and still be okay. After 3…dxc4 4.Bxb7 Nd7 5.Bxa8 Qxa8 6.f3 we reach the position below.
White has got an exchange for two pawns. So material can still be considered equal. But black is far ahead in development. White’s pieces are uncoordinated and hard to develop. After move 6, all of white’s pieces are still at the first rank!
Thus, black has a good game here.
Black plays 3…c6
If black is not confident about sacrificing an exchange, he can play 3…c6, simply defending the pawn.
White may try to attack the weak b7 pawn but as we will see, black can still retain a better game.
After 4.cxd5 cxd5 5.Qb3 Nf6 6.Qxb7 Nbd6 7.d4 Rb8 8.Qxa7 black has a beautiful move here. Try and find out black’s best move before reading further.
8…Qc8!!
Black attacks the c1 bishop at the same time threatening to trap the queen with Ra8!
Black has a winning position here. Now a normal move like 9.Nc3 will lose the queen due to 9…Ra8. And if 9.Bf4, then 9…e5! 10.dxe5 Bc5 11.Qa4 Rb4 and black wins the f4 bishop.
And if white plays 4.Qb3 directly, then after 4…e6 5.Qxb7 Nd7 6.Qxc6 Rc8 7.Qa6 Rxc4 black has a better game.
For example, after 8.Na3 Rc8 9.Qxa7 Bc5 black has more than enough compensation for the pawn.
White plays 2.h3
White can avoid Grob gambit and play 2.h3, simply defending the g4 pawn. But after 2…e5, black has a very good control of the center. A player from white side would never be happy with the position below after 2 moves.
After 3.Bg2, black can play 3…c6, 3…Nc6 or even 3…h5! Attacking the g4 pawn.
A sample line can go 3.Bg2 c6 4.d4 e4 5.c4 Bd6 6.Nc3 Ne7 7.Qb3 9-0-0 and black has a positional advantage.
Conclusion
Grob opening is clearly not preferable for white for any serious games. Because even after playing a gambit, white easily ends up in a worse position. Black can even sacrifice an exchange and be fine.
Thus, this opening is only recommended for blitz games or practice games with the idea to explore different set-up.