London System, with e6

The London System with e6 arises after 1. d4 d5 2. Nf3 e6 3. Bf4. Black has fixed the e-pawn before developing the king's knight. The position therefore differs from the main London (1. d4 d5 2. Nf3 Nf6 3. Bf4) mostly in move order. After the most common reply, 3...Nf6, it is identical to the main line with 3...e6. Playing 2...e6 first also leaves the Queen's Gambit Declined on the table should White choose c4. With 3. Bf4, White turns that route down and commits to the London scheme.

Black's pawns on d5 and e6 form a compact, resilient center. The familiar cost is that the c8-bishop stays behind the e6-pawn. The point of delaying ...Nf6 is flexibility. With the g8-knight still at home, Black can develop the dark-squared bishop to d6 at once, or strike with ...c5 before making any kingside decisions, and only then settle on a knight setup.

The three main replies differ clearly in intent. 3...Nf6 is the engines' first choice and simply transposes into standard London positions. 3...Bd6, chosen in about a quarter of games, places a bishop opposite White's f4-bishop and offers to trade the piece that anchors White's whole system. White then has to decide whether to exchange, retreat, or let Black take on f4. Black's practical results with this move are marginally the best of the three. 3...c5, played in roughly a fifth of games, attacks d4 immediately. It is the first step of the standard counterplan of pressure on the d4-pawn and the weakened b2-square. Engines also rate 3...Be7 highly, a quieter developing move that keeps all pawn-break options open.

The position ranks among the more frequently reached named lines, with close to 147,000 Lichess games. The engine considers it balanced, though White scores somewhat better in practice, about 51% wins against 44% for Black, with few draws. As in the London generally, play revolves around piece placement and the timing of pawn breaks rather than forcing theory.