The Khmer Republic was a former state in Cambodia leaded by the US-backed marshal Lon Nol between 1970 and 1975. The nation was formed after a coup on the royal government, which was led by Norodom Sihanouk on March 18th, 1970 due to his tolerance of North Vietnamese troops in Cambodia which held lots of control in most of Cambodia and a general worsening economy. The coup also saw the abolishment of the Cambodian monarchy, which would only be restored in 1993. On October 9th on the same year, the Khmer Republic was proclaimed and Cheng Heng became president.
Most of the history of the Khmer Republic saw it in war with the Khmer Rouge in the Cambodian Civil War. The United States severely backed the Khmer Republic, but still failed at preventing the Khmer Rouge from taking over Cambodia. On April 17th, 1975 Khmer Rouge troops entered the Khmer Republic’s capital, Phnom Penh. Lon Nol had already fled the country 16 days earlier.