U.S. Army is a military organization reporting to the department of defense. It conducts various operational and institutional missions. The organization includes corps, divisions, brigades and battalions that conduct a range of operations worldwide. It works towards providing the infrastructure necessary to raise, train, equip and deploy readiness of army forces. Its component United States Army Reserve provides trained soldiers and units with the capabilities necessary to support strategies during peacetime, contingencies and war. The organization s component Army National Guard is composed of traditional guardsmen civilians who serve the country, state and community on a part-time basis. It maintains a fleet of aircrafts, air defense artilleries, antiarmor weapons, indirect fire systems, and wheeled and tracked vehicles. U.S. Army also includes nuclear, biological and chemical defense systems.