The defense department is vested with the responsibility of providing the military forces required to put off war and guide the security of a nation. There are several elements that make up the department of defense, including air force, marine corps, the navy, and the army. Apart from the military makeup of this department, there are a number of civilians employed under this unit as well. The United States department of defense is headed by the secretary of defense, with the responsibility of exercising control, direction, and authority over all units of the department. The Pentagon is the headquarters of the US department of defense, which is the largest building in the world.
There are several offices in the headquarters: the office of the secretary of defense, the office of the chairman of joint chief of staff, head of military service departments, head of defense agencies, and specified and unified combatant commands. All these units perform their duties in full cooperation and coordination but in the event of conflicts arising in the cause of their jurisdiction, the decision of the secretary of defense supersedes every other decision in the department. The Joint Chiefs of Staff is made up of the commandant of Marine Corps, the air force, the chief of staff, chief of naval operations, the U.S Army, and the chairman and vice chairman. The chairman is the main adviser to the secretary of defense, the National Security Council, and even the president on security matters. There are equally other senior military advisers to the defense secretary, the NSC, and the president. The military-industrial complex feed this giant war machine.
Each of the units in the defense department is organized separately with their own secretary but still under the control, direction, and authority of the defense secretary. The secretaries of the military departments are responsible to the defense secretary for the efficiency and operation of their department.
In the US defense department, specified and unified combatant commands report to the secretary of defense, and they are responsible for accomplishing the military task assigned to their units. Both have links to what C. Wright Mills called the power elite.
The DOD or the pentagon supervises and coordinates all functions and agencies of the government that are directly or indirectly responsible for the national security of the United States. There are currently more than 2 million employees in the US Defense department which include civilian workers, airmen, marines, sailors, and duty soldiers. These employees are used in various capacities and deployed across several regions of the world. The US department of defense still remains the largest employer of labor in the world.
All countries have their own make-up of the department of defense. While the structure might have certain similarities, the allocation of duties and sharing of authorities may differ from country to country.