Which statement best describes Defense in Depth?

• A. Single-layer defense focusing on long-range fires.
• B. Rapid withdrawal to avoid engagement.
• C. High mobility with no fixed positions.
• D. Layered defense with multiple lines of defense.

Answer: (D)

Defense in depth is about layering your defenses across multiple lines so each layer slows, disrupts, and degrades an attacker, while buying time for you to react. In air defense, that means setting up forward, middle, and rear belts with overlapping sensors and fires, so if the enemy penetrates one layer, the next is ready to engage and preserve coverage. This approach creates redundancy—if one position is suppressed or bypassed, others continue to defend—so you don’t rely on a single barrier. It also allows fire to be shifted from one layer to another as the situation evolves, making the defense more resilient and flexible. The other descriptions describe a single-layer defense, a rapid withdrawal, or high mobility without fixed positions, which don’t capture the idea of multiple, interconnected lines of defense working together.