Which factor impedes High Angle Fire according to the effects of overhead clearance?

High Angle Fire relies on the projectile being able to reach its target at a steep trajectory, often requiring specific spatial allowances for the rounds to travel unobstructed. Overhead Interference refers to obstacles or structures above the firing line that can obstruct the path of the projectile as it ascends and descends during its high-angle trajectory.

When there are physical structures like trees, buildings, or other overhead obstacles, they can significantly affect the range and angle of fire, potentially causing the round to detonate prematurely or veer off target. This is particularly critical in High Angle Fire, where the launch angle is typically steep. Understanding the importance of clear overhead space is essential for effectively utilizing High Angle Fire, as these obstacles will limit the effective range and accuracy of the mortar rounds.

In contrast, while Mask Interference relates to being obstructed by terrain below, Ground Stability refers to how grounded the firing position is for maintaining accuracy, and Surface Conditions pertain to the characteristics of the ground on which the mortars are positioned—none of these factors directly affect the projectile's trajectory as overhead interference does. Thus, recognizing overhead interference as the primary issue is crucial for successful High Angle Fire operations.