What is the first phase of defense against an enemy?

The first phase of defense against an enemy typically involves understanding and responding to the threats posed by the enemy, which includes anticipating and preparing for their actions, such as an enemy preparation bombardment. This phase is crucial as it allows the defending force to gauge the enemy's intent and capabilities, while simultaneously assessing their own defensive posture.

In this phase, forces might improve their positions, fortify defenses, and carry out reconnaissance to gather intelligence. This preparation establishes a foundation for the defensive strategy. Once the enemy's actions are observed, the defending force can then transition into active defensive measures, such as opening fire or planning counter-offensive actions.

The other options represent subsequent actions or strategies that occur after initial enemy preparations are identified. Opening fire and fire control is a response to enemy action, while retrograde involves withdrawing from a position, and a counter-offensive is a more aggressive response to regain lost ground or momentum after the initial defensive phase has been breached. Understanding this sequence is critical for effective military strategy in defense scenarios.