Diagonal pressure

A diagonal is a line of same-colored squares. Diagonal pressure arises when a bishop or queen uses that line to attack a target, restrict movement, or make a future opening of the diagonal dangerous.

The pressure may be direct, with the target already visible, or latent. In the latent form, a pawn or piece stands between attacker and target, but an advance, capture, or the deliberate giving up of a pawn or piece, called a sacrifice, could remove the blocker. A long-range piece can therefore influence the position before it has an immediate threat.

Fianchettoed bishops, developed near a corner behind an advanced pawn, often work on long diagonals. A bishop and queen on the same diagonal can form a battery, meaning two aligned pieces concentrating their force. The pressure becomes especially serious when it points toward the king, a pawn that holds the position together, or a difficult-to-defend color complex.

What strengthens or reduces the pressure

• Opening the diagonal through exchanges or pawn breaks, meaning advances or captures that change the pawn arrangement.
• The number of attackers and defenders at the final target.
• Whether the blocker can move while creating a threat that forces the opponent to respond.
• Whether the bishop or queen has a secure square from which to maintain the line.

A long diagonal is not automatically powerful. If it ends at a well-defended piece, remains closed with no practical way to open it, or lets the attacker be driven away, the pressure may have no useful consequence.