“I have never advocated war except as a means of peace.”
-Ulysses S. Grant
Military service can be voluntary and involuntary. Although many countries have their military service made up of volunteers, in times of war, mandatory military service can be conscripted by governments to ensure that adequate numbers are available for national defense. Some countries have mandatory military service and require that all citizens serve for a period of time, for example, two years in active duty five years in the reserve. The United States does not have mandatory military service; however, on occasion its government has imposed a draft into military service.
The U.S. has several uniformed services that, throughout its history, have protected the country over land and sea, and in the air. These services are: the U.S. Army, Marine Corps., Navy, Air Force, Coast Guard, National Guard and the Public Health Service Commission Corps. Some branches of the U.S. military service date back to the Revolutionary War. The U.S. Army, for example, was first the Continental Army, founded in 1775 to fight in the Revolutionary war. The U.S. Navy and Marine Corps were also founded in 1775. Since its inception, young people have given their lives to preserve peace and security and to protect the United States.
The Pentagon located in Washington D.C. is the headquarters for the U.S. Department of Defense (D0D). The mission of the DOD is to provide the military forces needed to deter war and to protect the security of the U.S. The Department of Defense is the U.S.'s oldest and largest government agency. The DOD has 1.4 million men and women on active duty, and 718,000 civilian personnel. It is the nation’s largest employer. Another 1.1 million serve in the National Guard and Reserve forces.
(Source: The U.S. Department of Defense. http://www.defense.gov/about/#mission)