<p>The defenses of the bridge lay in depth along the approaches to, and the exits from, Hanoi: SAM sites, multiple batteries of automatic 23-mm flak, plus 37-mm, 57-mm, and 85-mm anti-aircraft artillery, radar-directed, massed and accurate. A few minutes' flight from Hanoi was the entire NVAF MiG inventory. As a final touch, there were radar-directed 85-mm batteries at each end of the bridge.
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<p>Into this potential death trap roared the bombing force, led by Colonel Robert M. White, a former X-15 research pilot. Behind him was his command, the 355th; further back in the formation was Olds' 8th TFW and the 388th TFW, led by Lieutenant Colonel Harry W. Schurr. They approached Hanoi from the northwest, crossing the Red River about 95 miles (150 km) out of town. They had been cruising at 500 kt (900 km/h); now they powered up to Mach 0.9 at their run-in altitude of 10,000 ft (3,050 m). At the northwest end of 'Thud Ridge', a major rock outcropping northwest of Hanoi, they changed course and headed for the bridge. MiGs from Phuc Yen airfield just north of the city tried for a head-on intercept and blew it, vanishing behind the task force. When White sighted the bridge, he turned the force south and began the climb to the bombing altitude of 13,000 ft (4,000 m). It was a struggle for the heavily loaded 'Thuds' to get up to that height, but they did. Then they peeled off in pairs, diving at the target in a 45-degree path that kept them in the run for seven long seconds while flak and missiles headed their way. They released their bombs between 7,000 and 8,000 ft (2,100 and 2,400 m), made the pullup and a hard turn downriver heading east. On their way, they reached and passed Mach 1; as they blasted over the 'Hanoi Hilton', the US prisoners there knew who was overhead by the characteristic sound of the 'Thud' in full afterburner and over the Mach. Later they would tell what a morale boost it was to hear that particular cacophony.
