Da Nang, South Vietnam's second most populous city, fell to Vietcong troops on Saturday, March 29, 1975. One would think that the South Vietnamese government would have fought bitterly for the city, as it paralleled San Francisco and Manchester in the stature it held in its country. However, by the time Da Nang fell, South Vietnamese resistence was crumbling.
Southern Vietnamese troops in the area were so intent on saving themselves that two entire infantry divisions dissolved, their members shedding their uniforms or attempting to escape via U.S. and Southern Vietnamese evacuation craft (naval and aeronautical). Some of these had originally been intended for civilians but were hijacked by desperate soldiers, who went so far as to hide in the wheel wells of the one cargo plane that made it into the city itself; those who found no room even there would lie down in the runway in an attempt to prevent take-off. Unfortunately for those left behind, the plane did take off, and several dozen soldiers were killed on the runway. Most if not all of the soldiers in the wheel well died or fell out of the plane en route to Saigon. One cannot blame them, however, for fleeing; they would most likely have been killed or tortured by the Vietcong intelligence and/or military.
The deterioration of a country's military and political command structure almost always directly precedes the fall of that country's soverignty. Rome's loss of contact with its western territories to Germanic tribes, the United States' loss of control of the southern states right before the Civil War, and Napoleon's loss of the allegience of Eastern Europe all directly preceded an immediate loss of territory to other political entities. In the case of the Vietnam War, the days before the fall of Saigon were marked by the desertion of Vietnamese people who did not want to face the consequences of being associated with the South Vietnamese government. Once Saigon couldn't control its own people, its fall was assured.