On 18 March, the Cambodian National Assembly officially deposed the Cambodian leader Norodom Sihanouk and named Lon Nol as provisional head of state. The North Vietnamese response to the coup was swift. Even before Lon Nol's March 12 ultimatum for PAVN and NFL forces to leave Cambodia, they had begun expanding their logistical system (the Ho Chi Minh trail) from southeastern Laos into northeastern Cambodia. After Sihanouk's overthrow and Lon Nol's anti-Vietnamese movements, PAVN launched an offensive (Campaign "X") against the Cambodian army. They quickly seized large portions of the eastern and northeastern parts of the country, isolating and besieging or overrunning a number of Cambodian cities, including Kampong Cham. Fearing a joint ARVN–Cambodian attack after the coup, COSVN was evacuated to the newly Vietnamese-controlled Kratié Province of Cambodia on March 19, 1970.