The US Department of the Army has its marching orders. The group represents one of the three US military departments -- along with the Air Force and Navy -- of the US Department of Defense. As part of its focus, the Army provides ground-based military forces to work to deter and fight wars in addition to protecting the security of the US. The Army has more than 675,000 soldiers, which includes both active duty soldiers and those who serve as reservists. Army personnel are deployed in about 80 countries. The military department operates about 40 forts throughout the US and extends its reach overseas to operate bases in Africa, Europe, Japan, the Middle East, and South Korea.