Weak square — what it means in chess
A square that cannot be defended by a pawn, often a home for an enemy piece.
A square that cannot be defended by a pawn, often a home for an enemy piece.
[[board startfen="rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1" caption="The Maroczy Bind: White grabs an imposing center with c4 and e4 — and in the same gesture gives up the d4 square forever. Both pawns that could have guarded it have marched past it." pgn="e4 c5 Nf3 Nc6 d4 cxd4 Nxd4 g6 c4" notes="Every pawn move is a trade: squares gained ahead, squares abandoned behind. Watch d4. White stakes the first claim. The Sicilian. White develops. Black hits d4 from the flank. White opens the center. Black trades. The knight recaptures — no White pawn stands on d4 now, remember that. Black prepares the long-diagonal bishop, whose favorite square is about to appear. The bind: c4 and e4 clamp down on d5 and smother Black's breaks. And the price is on the board — with both the c- and e-pawns past the third rank, no White pawn can ever attack d4 again. The square is a hole, and Black's entire setup will orbit it."]]
A weak square is a square that can no longer be defended by pawns — a hole, in Nimzowitsch's word — created the moment the pawns that could have guarded it advance past it or disappear. Pieces can still defend the square, but pieces tied to guarding a square are pieces not doing anything else, which is why the weakness is permanent in a way piece placements never are: pawns do not walk backward.
The position above makes the accounting visible. The Maroczy Bind is a good structure for White — the c4/e4 clamp is one of the most respected space arrangements in chess — and it still pays the toll: d4 becomes a hole the instant c4 lands, and generations of players have built Black's whole game around occupying it. That is the mature way to think about weak squares: not as blunders but as prices. Every pawn advance buys something ahead and abandons something behind, and the question is always whether the purchase covers the bill.
The Endgame Society glossary defines more than 240 chess terms — rules, notation, tactics, strategy, pawn structures, endgames, and openings — in language a beginner can act on rather than dictionary shorthand.