Which type of fire is designed to impede enemy movement across defensive lines or areas?

The type of fire that is specifically designed to impede enemy movement across defensive lines or areas is referred to as Final Protective Fire. This fire mission is utilized as a last line of defense when enemy forces are anticipated to breach protective barriers. It involves the rapid delivery of artillery fire onto a designated target area to create a defensive posture that disrupts the enemy's advance and ensures that they cannot effectively maneuver or infiltrate friendly positions.

Final Protective Fire serves as a deterrent and a protective measure, aiming to create chaos and destruction among advancing enemy troops, thereby slowing or halting their movement. This is particularly important in defensive operations where maintaining control over territory is critical. By focusing artillery fire in a timely manner on specific areas, it enhances the overall defensive capabilities of ground forces and aids in the protection of friendly units.

In contrast, the other options are employed for different purposes, such as immediate suppression for urgent threats, priority targets for high-value targets, and on-call targets for situations that arise dynamically during operations.