What is a major advantage of a linear defense?

A linear defense primarily offers strong mutual support among units positioned along the defense line. This structure allows for overlapping fields of fire, enabling different units to cover each other effectively. When one unit comes under attack, adjacent units can provide assistance, reinforcing the defense and potentially overwhelming the attacking force. This mutual support is crucial, especially in maintaining cohesion and stability in the face of enemy advances.

In contrast, the other options emphasize different aspects of a defensive posture. Increased flexibility may be more characteristic of a dispersed defense, where units can reposition as necessary. Reduced enemy visibility and better concealment are more often associated with terrain utilization and tactical positioning rather than the linear formation itself. A linear defense, while it effectively allows for strong mutual support, does not inherently improve reduced visibility or concealment. Thus, mutual support stands out as the key advantage in this defensive arrangement.