What is the Army?

The United States Army is the unified land warfare force of the United States military. By order of precedence, the Army is the most senior branch of the military. Considering themselves descended from the Continental Army, the Army was established on 14 June 1775 by order of the Continental Congress. After the war, the Army was officially reformed as an extension of the new United States Government under the Articles of Confederation in 1784. 
The Army is the single largest military branch, with fiscal year 2017 census showing the Active component numbering 476,000, the Reserves at 199,000, and the Army National Guard at 343,000. The Department of the Army says that the mission of the Army is to "to fight and win our Nation's wars, by providing prompt, sustained, land dominance, across the full range of military operations and the spectrum of conflict, in support of combatant commanders".
The Army conducts missions word wide, from South America to Africa to Europe.