Four Knights Game

Copy for copy, you are always one move ahead. Cash that in, don't rush it.

Black often mirrors you: ...Nc6, ...Nf6, ...Bb4, ...O-O, ...d6. That is fine. Every mirror leaves you with the move, and in a symmetrical position the side with the move is the one who gets to change the structure first: Bg5, Nd5, or the d4 break. Finish development, then choose.

Bb5 pins the knight that guards e5 and clears the way to castle.

On b5 the bishop does two jobs at once. It ties the c6-knight to the king so e5 has one defender fewer, and it empties f1 so you can castle on the very next move. Bc4 looks more aggressive but runs into the fork trick ...Nxe4 and ...d5.

Bishop on c5 with no ...Nf6 yet? Nxe5, then d4 forks and wins the piece back.

After 3...Bc5 you can play Nxe5. If Black takes back ...Nxe5, d4 attacks both the bishop and the knight, and you regain the piece with a big centre. If Black tries ...Bxf2+ instead, Kxf2 Nxe5 d4 leaves material level and Black's knight running. It only works while e4 is still defended by your c3-knight and nothing of yours is loose.

When ...Bb4 pins c3, e4 is loose. Castle to break the pin before opening up.

The c3-knight guards e4, but a pinned piece cannot move, so once ...Bb4 lands your e4-pawn is effectively undefended. That is why you play d3 and not d4 in the main line, and why castling comes first. If the bishop takes on c3, bxc3 gives you two bishops and a half-open b-file for the rook.

After d3, Bg5 pins the f6-knight so Nd5 lands with real force.

Black's only freeing idea is ...d5. Bg5 pins the knight that would support it, and then Nd5 jumps into the hole with the knight and bishop both aimed at f6 and the black king. Black usually has to give up the b4-bishop to remove your c3-knight, which hands you the two bishops.

Prefer open positions? 4.d4 is the Scotch Four Knights: trade on d4, then Nxc6.

Instead of Bb5 you can strike with d4 at once, before Black has a bishop on b4. After ...exd4 Nxd4 Bb4 you play Nxc6 bxc6 Bd3 and the game is about Black's doubled c-pawns. It is a sound, honest alternative and a good change of pace if opponents keep mirroring you.

Finish developing, then break the symmetry: Nd5, Bxc6, or a prepared d4.

You do not need a knockout. Get castled, put the dark bishop on g5 or e3, and connect the rooks. Then pick the change of structure that suits the position: Nd5 into the outpost, Bxc6 to give Black doubled pawns, or d4 once the c3-knight is no longer pinned. Trade into an endgame where your structure is cleaner and grind.