Facing the London System: Black Replies to 4.c4 Against ...h6

The London System's signature idea is a solid pawn centre and a quick kingside attack. By playing 3...h6 you've prevented Bg5 or any immediate Bxf6 ideas, but it comes at a cost: you've spent a tempo on a non-developing move. When White hits you with 4.c4, they're immediately challenging your centre and asking whether your ...h6 was worth the time. Your job is to complete development smoothly and prove the pawn on h6 isn't a weakness later. The most principled way to do that is with ...e6, building a classical pawn chain and freeing your light-squared bishop.

Stockfish's top recommendation is 4...e6, played over 3,400 times in the database. From here the natural continuation is 5.Nc3 Bd6 6.Bxd6 Qxd6 — you trade off White's active bishop and reach a solid, if slightly passive, position. After this exchange White's bishop pair is gone, and you have a clean structure with no immediate weaknesses. The engine still favours White (+0.43), but you've avoided any major pitfalls. Your queen sits comfortably on d6, and you can follow up with ...0-0, ...b6, and ...Bb7 to challenge the centre. This is the safe, sound path that minimises your opponent's advantage.

Not every Black player chooses ...e6. Here's what the database reveals about the top alternatives after 4.c4, and how White scores against each one: 4...Bf5 (2,052 games, White 51.7%) — a natural developing move, but it leaves the c8-bishop exposed to an early Nh4 or g4 push. 4...dxc4 (1,938 games, White 55.2%) — giving up the centre immediately scores worst of the popular moves; White recaptures with e3 or Qa4+ and enjoys a space advantage. 4...Nc6 (1,493 games, White 54.7%) — an active-looking move but it doesn't address the centre, and White can play cxd5 or e3 and keep a comfortable edge. 4...c6 (1,239 games, White 55.0%) — solid but passive; White keeps a grip on the centre. In every case, White scores above 50%, but ...e6 keeps it closest to equality.

The clearest known mistake here is 4...Bg4. This move is tempting — you pin the knight on f3 and prevent e4 — but the statistics have flagged it as an inaccuracy that costs roughly 0.8 pawns compared to the best move. White can simply play 5.Nbd2 or 5.Nc3, and your bishop on g4 lacks a good square if White pushes h3. Meanwhile, White's centre remains unchallenged. The engine says you should have played ...e6 instead. Avoid 4...Bg4 unless you have a very specific follow-up in mind; in most club games it just leaves you a tempo down with a misplaced bishop.