strength in Saigon had almost been restored to its previous high level. Westmoreland warned his superiors that the enemy might attack before or after the Tet holiday, which would last seven days starting 30 January, but he doubted that they would violate the traditional holiday truce itself.
On 20 January the enemy started their final diversion: a bombardment of the U.S. Marine Base at Khe Sanh in northern I Corps Zone. This siege continued some eleven weeks, well beyond the collapse of the Tet offensive, and demanded a large-scale rescue effort by U.S. forces in the north. On the morning of 30 January, the start of the Tet holiday, some Viet Cong units prematurely attacked seven cities. The main enemy attacks began the next day throughout the country and continued through 11 February. Although the allied command on 30 January cancelled all holiday leave for military personnel, few soldiers returned to their posts quickly enough to help stem the main attacks. The enemy failed to provoke a national uprising, and suffered heavy losses. But the Tet offensive damaged many allied, especially South Vietnamese, facilities and caused thousands of allied civilian and military casualties.
Enemy attacks on allied bases quickly drew Dust Off into the thick of the fighting. In the north the 43d Medical Group suffered damage to many of its dispersed aircraft. All medical units, both north and south, had been warned at least a few hours in advance to expect heavy casualties, but the offensive still almost swamped all allied hospitals and clinics. On 1 February the 43d Medical Group, with the 44th Brigade's approval, requested a C-141 for a special mission, evacuating as many U.S. casualties as possible from the 6th Convalescent Center, the 8th Field Hospital, and the 91st Evacuation Hospital, to make room for the continuing influx of wounded. CH-47 Chinook helicopters evacuated many patients between hospitals and casualty staging facilities.
On 1 February the 44th Medical Brigade's aviation officer told the various medical groups that all helicopter ambulance detachments were limited to twelve pilots, regardless of any other authorization. Both pilots and machines had become critically short. If any of the 43d's detachments should run into severe problems, it was to turn to the 55th Group and the 498th Medical Company. Later the 43d Group did have to call on the 55th Group for substitute aircraft. Only the somewhat sporadic nature of the fighting allowed the medical system to keep up with the inflow of patients.
At the start of the Tet offensive, the air ambulance detachments in the south were no better prepared for the onslaught of wounded than those in the north. The 44th Brigade began to keep constant watch on the status of the aircraft with each detachment so it could redistribute the flyable aircraft to the detachment in greatest need. But fighting
