Against 1...d5

The idea

After 1.d4 d5 2.Nf3 Nf6 3.Bf4, White has the London's key move in. Black chooses between the solid ...e6 with ...Bd6 and ...c5, and an early ...c5 that goes after d4 and b2 straight away.

Plans for White

Continue with e3, c3, Nbd2 and Bd3, and castle. Keep d4 solid and the bishop on f4 safe, and look for Ne5 once the setup is complete. Playing c4 instead of c3 transposes to the Queen's Gambit, if White wants a sharper game.

Plans for Black

Develop with ...e6 and ...Bd6 to challenge the bishop on f4, or play ...c5 at once to strike at d4. Either way, ...c5 and ...Nc6 are Black's main ways to put pressure on White's center.

Watch out for

For White, an early ...c5. Wikipedia notes that 2.Nf3 c5 3.Bf4 cxd4 4.Nxd4 Nd7 "may already be better for Black" in another move order, one reason many players play 2.Bf4 first.

For Black, letting White's knight settle on e5 without a fight. Plan ...Nd7 or ...Nc6 to challenge it.