The Khmer Rouge Empty Phnom Penh

By early 1975, the Khmer Republic faced an existential crisis as insurgent Khmer Rouge forces tightened their encirclement of Phnom Penh. The government of the United States-supported republic had lost control of most surrounding territories, retaining only the capital and isolated provincial centers. Crucial river convoys traveling up the Mekong River from South Vietnam were severed by naval mines and insurgent ambushes along the riverbanks, forcing the regime to abandon waterborne logistics in mid-February. Phnom Penh was left entirely dependent on an emergency aerial resupply through Pochentong Airport, operated by the contracted company BirdAir, while hundreds of thousands of displaced civilians poured into the beleaguered city.

The military situation unraveled rapidly as the dry season progressed. President Lon Nol resigned on 1 April and departed into exile, leaving leadership to an interim administration that hoped in vain to open negotiations. That same night, the strategic Mekong outpost of Neak Luong fell after a three-month siege, freeing thousands of insurgent fighters and captured heavy artillery to reinforce the assault on the capital. Despite sporadic counterattacks by republican divisions, front lines to the north and west collapsed under steady artillery and ground pressure, compressing defensive lines into the city outskirts.