On 25 December 1978, the Vietnamese Army launched its full-scale invasion. Its columns initially advanced into north-east Cambodia, taking Kratie on 30 December and Stung Treng on 3 January. The Vietnamese main force then entered Cambodia on 1 January 1979, heading along Highways one and seven toward Phnom Penh. Cambodia's forward defences failed to stop them. With an attack on Phnom Penh imminent, in January Pol Pot ordered Sihanouk and his family to be sent to Thailand. The entire diplomatic corps followed shortly after. On 7 January Pol Pot and other senior government figures left the city and drove to Pursat. They spent two days there before moving on to Battambang.