On the Tet holiday, Vietcong units surge into action over the length and breadth of South Vietnam. In more than 100 cities and towns, shock attacks by Vietcong sapper-commandos are followed by wave after wave of supporting troops. By the end of the city battles, 37,000 Vietcong troops deployed for Tet have been killed. Many more had been wounded or captured, and the fighting had created more than a half million civilian refugees. Casualties included most of the Vietcong's best fighters, political officers and secret organizers; for the guerillas, Tet is nothing less than a catastrophe. But for the Americans, who lost 2,500 men, it is a serious blow to public support.