A national army is a military force organized and maintained by a sovereign state to defend its territory and interests. These armies are typically composed of professional soldiers, reservists, and volunteers, and they operate under the authority of the government. National armies are responsible for protecting the nation from external threats and may also assist in domestic emergencies. In addition to defense, national armies often participate in international peacekeeping missions and humanitarian efforts. They may engage in training exercises with other countries' military forces to enhance cooperation and readiness. Examples of national armies include the United States Army, the British Army, and the Indian Army.