United States Guards (1917)

The United States Guards (USG) was a lightly armed, all-infantry military force maintained by the United States from 1917 to 1919. Tasked with an internal security and territorial defense mission within the Zone of the Interior, it was used to protect critical infrastructure and suppress civil unrest during World War I. Though it successfully defended more than 300 strategic sites during its brief existence, its use as a provost force was marked by violent clashes and the liberal use of lethal force. During a deployment in Butte, Montana, the United States Guards was accused by Thomas Watt Gregory, the Attorney-General of the United States, of imposing a "reign of terror" upon the city.

A component of the National Army, the United States Guards was composed of men over the age of 30 recruited from military veterans, police officers, and firefighters. At its largest, it consisted of approximately 28,000 personnel organized in 43 battalions.