Weak square

A weak square, also called a hole, usually appears when the pawns that could control it advance, capture, or disappear. Because pawns cannot move backward, the loss of control may last for the rest of the game. The opponent may try to occupy the square, use it as an entry route, or build threats around it.

The pawn-based definition is useful, but practical accessibility is decisive. A square may lack pawn defense yet cause no problem if no enemy piece can reach it, if occupation attacks nothing, or if the defender can exchange the invader immediately. A theoretical defect is not always a relevant weakness.

Defending a square that pawns cannot cover

• Control it with pieces and prevent favorable occupation.
• Exchange the piece that intends to settle there.
• Create counterplay, meaning active threats of your own elsewhere, so the opponent has no time to maneuver.
• Use prophylaxis, meaning anticipation and prevention of the opponent's plan.

From the attacker's viewpoint, a weak square may become a strong square or an outpost. These terms describe the same area from opposite perspectives: the defender's defect and the attacker's opportunity.