DOS meaning in Military and Defence ?

The United States Department of State (DOS), or State Department, is an executive department of the U.S. federal government responsible for the nation's foreign policy and international relations. Equivalent to the ministry of foreign affairs of other nations, its primary duties are advising the U.S. president, administering diplomatic missions, negotiating international treaties and agreements, and representing the U.S. at the United Nations. The department is headquartered in the Harry S Truman Building, a few blocks from the White House, in the Foggy Bottom neighborhood of Washington, D.C.; "Foggy Bottom" is thus sometimes used as a metonym.

Established in 1789 as the first administrative arm of the U.S. executive branch, the State Department is considered among the most powerful and prestigious executive agencies. It is led by the secretary of state, a member of the Cabinet who is nominated by the president and confirmed by the Senate. Analogous to a foreign minister, the secretary of state serves as the federal government's chief diplomat and representative abroad, and is the first Cabinet official in the order of precedence and in the presidential line of succession. The position is currently held by Antony Blinken who was appointed by President Joe Biden and confirmed by the Senate on January 26, 2021 by a vote of 78–22.

As of 2019, the State Department maintains 273 diplomatic posts worldwide, second only to China's Ministry of Foreign Affairs. It also manages the US Foreign Service, provides diplomatic training to US officials and military personnel, exercises partial jurisdiction over immigration, and provides various services to Americans, such as issuing passports and visas, posting foreign travel advisories, and advancing commercial ties abroad. The department administers the oldest US civilian intelligence agency, the Bureau of Intelligence and Research, and maintains a law enforcement arm, the Diplomatic Security Service.