Date Founded: August 10th , 1949

Current head of the department : James N. Mattis

The Department of Defense is an executive branch department of the federal government of the United States charged with coordinating and supervising all agencies and functions of the government concerned directly with national security and the United States Armed Forces. The Department is the largest employer in the world, with nearly 1.3 million active duty servicemen and women as of 2016. Adding to its employees are over 801,000 National Guardsmen and Reservists from the four services, and over 740,000 civilians bringing the total to over 2.8 million employees. It is headquartered at the Pentagon in Arlington, Virginia, just outside of Washington, D.C .One of the Largest buildings , built during the early years of World War 2 , still one of the most efficient office buildings in the world. The United States’ Military and Department of Defense make up a huge portion of our country’s expenditures and has greatly influenced our government and citizens. The Army was in charge of exploring and mapping much of America , about 15, 654 square miles occupied by the facilities and U.S. bases.