Averbakh System (3.c4 d6)

The idea

After 3.c4 d6 4.Nc3, White has pawns on c4, d4 and e4. Wikipedia names this the Averbakh System, and 365chess notes it's likely to transpose into the King's Indian Defense if Black plays ...Nf6.

Plans for White

Develop with Nf3 or Be3 and Be2, castle, and use the space. White can push d5 to cramp Black, or keep the center and develop. The c4 pawn gives White a Maróczy-like grip on d5.

Plans for Black

Strike at the center with ...e5 or ...c5, and develop with ...Nc6 or ...Nd7 and ...Nf6. Black can also choose setups without ...Nf6, such as ...Nc6 and ...e5, to keep the bishop on g7 free.

Watch out for

For Black, being squeezed. White's space is big, and if Black doesn't break with ...e5 or ...c5, White can play d5 and get a lasting edge.

For White, the d4 pawn and the long diagonal. ...e5 or ...c5 can open lines for the bishop on g7, so keep d4 protected.