World War I: The Selective Service Act of 1917 is passed, giving the President of the United States the power of conscription.

World War I or the First World War, also known as the Great War, was a global conflict between two coalitions: the Allies and the Central Powers. Main areas of conflict included Europe and the Middle East, as well as parts of Africa and the Asia-Pacific. There were important developments in weaponry including tanks, aircraft, artillery, machine guns, and chemical weapons. One of the deadliest conflicts in history, it resulted in an estimated 30 million military casualties, plus another 8 million civilian deaths from war-related causes and genocide. The movement of large numbers of people was a major factor in the deadly Spanish flu pandemic.

The Selective Service Act of 1917 or Selective Draft Act authorized the United States federal government to raise a national army for service in World War I through conscription. It was envisioned in December 1916 and brought to President Woodrow Wilson's attention shortly after the break in relations with Germany in February 1917. The Act itself was drafted by then-Captain Hugh S. Johnson after the United States entered World War I by declaring war on Germany. The Act was canceled with the end of the war on November 11, 1918. The Act was upheld as constitutional by the United States Supreme Court in 1918.

The president of the United States (POTUS) is the head of state and head of government of the United States. The president directs the executive branch of the federal government and is the commander-in-chief of the United States Armed Forces.

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; this was the country's first peacetime draft.