Which military tactic is directly linked to isolating an enemy unit?

The tactic that is directly linked to isolating an enemy unit is encirclement. This military strategy involves surrounding the enemy force on all sides to cut off their supply lines, reinforcements, and escape routes. By doing so, the encircled unit becomes isolated and unable to communicate or coordinate effectively with other units, leading to a decline in morale and combat effectiveness. Encirclement allows the attacking force to gain a significant tactical advantage, making it difficult for the enemy to regroup or launch a counterattack.

Other options, such as retreat and fighting withdrawal, focus on preserving one's own forces rather than actively isolating the enemy. The head-on assault is an aggressive tactic aimed at directly engaging the enemy but does not necessarily involve isolation as a primary objective. Therefore, encirclement is the most fitting answer, as it is specifically designed to isolate and neutralize enemy forces.