Front for National Salvation - KNUFNS was proclaimed in a rubber tree plantation amid rigid security provided by heavily armed Vietnamese units reinforced with anti-aircraft guns. Vietnamese invasion of Cambodia The establishment of KNUFNS made a forceful removal of Democratic Kampuchea inevitable. However, KNUFNS was by no means an effective force. Only Vietnam's NVA, which had already had deployed a task force beyond the border, was capable of successfully completing such an operation. Twelve to fourteen divisions and three Khmer regiments - the future nucleus of KPRAF - launched an offensive on 25 December 1978, with a total invasion force comprising some 100,000 troops. NVA forces first headed towards Kratié City and Stung Treng City; however, this initial move was conducted to conceal their final strategic objectives: to secure a far-reaching Vietnamese base in the large but sparsely occupied North-Eastern territories, and to prevent any Khmer Rouge units from retreating into this area. The Khmer Rouge concentrated defensive units only in the plains regions of eastern and south-eastern Cambodia, where they correctly anticipated the main focus of NVA attacks. Strong Vietnamese forces rushed in three columns towards the Kampong Cham river port, the Mekong river crossing at Neak Loeung, and along the gulf coast in order to capture the sea ports of Sihanoukville and Kampot. The morale and combat effectiveness of the Democratic Kampuchea troops had considerably deteriorated, and many senior commanders had been lost in party purges. Serious battle engagements were confined to small areas as most Khmer Rouge units – under relentless NVA artillery and air force assaults – soon retreated west. The first Vietnamese troops reached the eastern banks of the Mekong near Phnom Penh on 5 January 1979. Whether it was Hanoi's initial intention to go any further is still not entirely clear. However, after a 48-hour halt to regroup and rout Khmer Rouge troops, the assault on Phnom Penh was launched, and the undefended and deserted city was captured on 7 January 1979. With the capital secure, NVA units proceeded towards and captured Battambang and Siem Reap in western Cambodia. Prolonged and serious fighting took place west of Sisophon near the Thai border, lasting until April. The last Khmer Rouge fighters evacuated into the remote forests on both sides of the border. Vietnamese troops did not advance further and kept a distance to Thai territory. As international dissent over the legitimacy of the new government