United States Coast Guard Port Security Units are deployable specialized units organized for sustained force protection operations. They can deploy within 96 hours and establish operations within 24 hours of arrival. PSUs conduct OCONUS port security in support of requesting regional Combatant commander. They provide Anti-Terrorism and Force Protection missions which include harbor and port defense, Humanitarian aid, coastal surveillance, and special missions. PSUs usually operate in U.S. territorial waters under the direction of the Coast Guard's command, but can quickly be called upon the Department of Defense request.