Detection of infiltration from the enemy is a purpose of a __________ patrol.

A security patrol is primarily designed to detect enemy infiltration and provide early warning of potential threats. By conducting security operations, units can gather intelligence on enemy movements, identify possible entry points, and monitor the surrounding area to ensure the safety of friendly forces. This type of patrol plays a crucial role in maintaining situational awareness and contributing to the overall defense strategy by acting as the first line of defense against enemy actions.

In contrast, a contact patrol is focused on making contact with the enemy and engaging them directly rather than merely detecting their movements. A raid involves a quick and purposeful attack on an enemy position, usually with the intention of causing damage or gathering intelligence but not for the ongoing surveillance aspect. An ambush is a tactic employed to surprise and attack an enemy force, but it does not involve the continuous monitoring or detection of infiltration that a security patrol is specifically tasked to accomplish.