4-44. A defensive mission generally imposes few restrictions on a defending commander. It allows freedom of maneuver within assigned boundaries, but it requires commanders to prevent enemy penetration of their rear boundary. Defending an AO is a typical mission for battalion and higher-echelon units. This mission allows commanders to distribute forces to advantageously use the terrain and plan engagement areas that integrate direct and indirect fires. Commanders ensure that subordinate unit defensive plans are compatible and that control measures, such as contact points and phase lines, are sufficient for flank and rear coordination when assigning AOs. The defensive plan addresses what happens when friendly forces succeed and gain an opportunity to transition from defensive operations to offensive operations.