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erted pressure on the government positions in and around Phnom Penh, and on the cities located in the surrounding provinces. At first glance, the attack seemed to indicate that nothing had changed in the Communist plan. Capture of the capital was still the ultimate objective and all offensive efforts centered around that purpose. Then gradually over the next few days subtle changes began to emerge. As combat activity intensified, government outposts guarding the Mekong River supply line also came under fire.
On 12 January, the Communists attacked Neak Loung, strategically the most critical outpost, located 38 miles downriver from Phnom Penh. Fighting escalated in the battle for the town, for its loss would seriously jeopardize and possibly end resupply by river.10
The vital convoys using the Mekong to transit from South Vietnam'to Phnom Penh quickly began to feel the effects of the escalation. They suffered from ever-increasing amounts of ground fire directed at them from the riverbanks. During the third week of January, two small convoys reached Phnom Penh. The ships had suffered considerable damage from insurgent fire received during the 62-mile trip from the Vietnamese border to the capital. On 27 January, two tankers and five ammunition barges made it to the docks of Phnom Penh. These ships, the only ones of a 16-vessel convoy to survive the deadly fire incurred during their journey up the Mekong, bore battle scars attesting to the feat. Their superstructures and hulls displayed marks caused by rockets, bullets, and shells.
While the river outposts and convoys endured this harassment, the Communists subjected Phnom Penh and its vital Pochentong Airfield to rocket and artillery fire. Although the volume was considerably less than that experienced during the 1974 offensive, it seemed to confirm that once again a frontal assault on Phnom Penh would serve as the centerpiece of the 1975 offensive. Gradually, the Lon Noi government realized that this assessment was incorrect. The Communists had intentionally reduced the amount of artillery and rocket fire directed at Phnom Penh. The Khmer Rouge had aimed its latest offensive not at the capital, but instead at its supply lines. Specifically, the Communists had decided to attack the convoys which carried 80 percent of the city's supplies. Siege warfare had returned.
To the government forces a siege did not seem to offer a serious threat because since the short-lived Communist interdiction of 1973, at least three river convoys had always reached the Cambodian capital in any one-month period. Unfortunately, the government experts were wrong. The convoy which limped into Phnom Penh on 27 January would be its last.
Less than a week later, the Khmer Rouge inflicted the mortal blow. Returning empty to South Vietnam from Phnom Penh, a convoy of supply ships struck a minefield, sown days earlier by Cambodian insurgents. The explosions ripped the ships apart creating a scene of death and destruction which literally made the river impassable. Thus 46 miles from Phnom Penh, In the vicinity of Phu My where the Mekong narrows to gain its strength before a long journey to the sea, a weakened and hungry Khmer Republic suffered a casualty from which it would not recover. The Com-munisrs had ended resupply by convoy.11
The laying of mines across a river in and of itself could not have ended convoy resupply. Minesweeping offered an excellent means by which to counter this threat and eliminate the potentially damaging effects of a blockade. Yet in this instance Cambodia became the exception, not the rule, because sweeping the Mekong of mines presented the Cambodian Navy with a formidable task. Normally a complex and dangerous maneuver, Communist control of the riverbanks made minesweeping nearly impossible and, ar best, very costly. The Republic's navy did possess a limited ability to sweep minefields, but the Khmer Rouge's use of command-detonated mines significantly reduced that marginal capability. The method of sweep used to eliminate these type mines entailed dragging the river's shallow water near its banks. This action would expose the command wires, allowing them to be severed. Once the wires were cut then the mine could be disarmed. In order to conduct this type of minesweeping operation, it was necessary to have control of the areas adjacent to the river. Without it, the minesweeping forces risked the prospect of being blown out of the water or captured. Neither option was a tactically sound alternative. Left with few choices, the government forces discontinued minesweeping operations. This decision guaranteed the convoy operators an extremely hazardous and nearly impossible journey. The sunken supply ships at Phu My stood as a stark testament to the futility of trying to mn the blockade.
The ensuing government attempts to reopen the river only served to diminish its forces and were too little, too late. The isolated garrisons throughout the countryside, already seriously undermanned, suffered additional losses when many of their men were redeployed and ordered to Join the battle to keep the Mekong open. Not only did these actions weaken the
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