In the United States, military conscription, commonly known as the draft, has been employed by the U.S. federal government in six conflicts: the American Revolutionary War, the American Civil War, World War I, World War II, the Korean War, and the Vietnam War. The fourth incarnation of the draft came into being in 1940, through the Selective Training and Service Act. It was the country's first peacetime draft. From 1940 until 1973, during both peacetime and periods of conflict, men were drafted to fill vacancies in the U.S. Armed Forces that could not be filled through voluntary means. Active conscription in the United States ended in 1973, when the U.S. Armed Forces moved to an all-volunteer military. However, conscription remains in place on a contingency basis and all male U.S. citizens, regardless of where they live, and male immigrants, whether documented or undocumented, residing within the United States, who are 18 through 25 are required to register with the Selective Service System. United States federal law also continues to provide for the compulsory conscription of men between the ages of 17 and 45 and certain women for militia service pursuant to Article I, Section 8 of the United States Constitution and 10 U.S. Code § 246. History Colonial to 1862 In colonial times, the Thirteen Colonies used a militia system for defense. Colonial militia laws—and after independence those of the United States and the various states—required able-bodied males to enroll in the militia, to undergo a minimum of military training, and to serve for limited periods of time in war or emergency. This earliest form of conscription involved selective drafts of militiamen for service in particular campaigns. Following this system in its essentials, the Continental Congress in 1778 recommended that the states draft men from their militias for one year's service in the Continental Army; this first national conscription was irregularly applied and failed to fill the Continental ranks. For long-term operations, conscription was occasionally used when volunteers or paid substitutes were insufficient to raise the needed manpower. During the American Revolutionary War, the states sometimes drafted men for militia duty or to fill state Continental Army units, but the central government did not have the authority to conscript except for purposes of naval impressment. Post Ratification of the Constitution, Article I.8.15, allows for Congress to conscript. Giving it the power to provide for calling forth the Militia to execute