"Why haven't they opened fire?"
In their command vans, the North Vietnamese missile crews were trying to track the B-52s on their Spoon Rest acquisition radars by following the jamming strobes, rather than using their Fan Song radars because turning on the Fan Song signal would expose them to attack by anti-radiation missiles from Wild Weasels. But the passive tracking was not working—the jamming was too intense.
As the raid approached, Nguyen Chan, commander of the 78th Battalion, saw "wave after wave of jamming—looking like large blades of a hand fan overlapping and slanted—came together, wiping out the whole spectrum…. It was so bright it hurt the eyes…. [The returns were] twisted and coiled together into a clump like a tangled ball."
Chan had his Fan Song tracking radar in standby, and all that was necessary was to press the Target Transmitter button and in four seconds the radar would be at full power. As the B-52s approached, Chan's search radar remained useless; watching his assigned target approach on the plotting board, he decided to turn on his Fan Song to look for the B-52s. There was considerable risk to this—the longer the Fan Song was on the air, the more likely it was to be attacked—but Chan took the risk and pushed the radar switch, using the range and bearing to the oncoming bombers, as plotted manually on the map, to point the antenna. Soon his fire control officer, Nguyen Van Luyen, was able to break out a single B-52 jamming strobe. Luyen put his crosshairs on the strobe and pushed the transfer button, and the target appeared on the scopes of the three guidance officers. The range guidance officer, Dinh Trong Due, excitedly called out "B-52!" and the three officers adjusted their range, azimuth, and elevation sets so the strobe was steady. Then they gently began to move their control wheels to follow the strobe.
Due continued to shout "It's really a B-52!" and Chan tried to quiet him so the crew would stay calm and concentrated. The jamming prevented the crew from going to the most accurate mode of the Fan Song, automatic track, but finally, at 7:49, Chan gave the order to fire; two buttons were pushed and, with their booster rockets burning brightly, two missiles climbed through the overcast toward their targets. The commander of the Hanoi Air Defense Force, Major General Tran Nhan, recalls that when Chan reported the firing to the 257th's regimental HQ, "sighs of relief could be heard at command headquarters from all levels."
One former North Vietnamese officer explained this phenomenon to me. "Firing back gives one a sense of power, a sense that one is fighting back and is not a passive victim," he said. "We gave everyone a gun and encouraged them to fire at American aircraft, no matter how far away. The people had to feel they were fighting back. We especially wanted the children in the air raid shelter to see their parents at the shelter entrance firing at the enemy."
A few miles north of Hanoi, Nguyen Thang, commander of the 59th Missile Battalion, was having a frustrating evening. The battalion had fired four missiles but all had missed, and dirt and gravel had showered down on the roof of the van from nearby bomb explosions. Now Thang was watching the raid approach both on his Spoon Rest radar scope and the plotting board next to the scope when he heard the call from the 261st's regimental headquarters alerting him to a target—T671—at an altitude of 10,000 meters.
Thang called to the fire control officer, Duong Van Thuan: "Target azimuth 350, distance 30 kilometers, altitude 10,000 meters, grouped."
Thuan manually turned the antenna to an azimuth of 350 degrees, then pushed the Target Transmitter buttons, and four seconds later the Fan Song radar was fully active. He saw heavy jamming on the scope, indicating a cell of three B-52s. He called back to Thang: "Target detected, azimuth 352, unknown range, altitude 10,000 meters, group, hostile."
Thang looked over at the fire control officer's radar scope, then back to his own, then at the plotting board, and ordered Thuan to prepare to fire two missiles. Although only azimuth and elevation were known, the third point—range—was easy to calculate. B-52s always flew between 30,000 and 38,000 feet. Finding range was simply a matter of elementary geometry: of using a side (altitude) and two known angles of a right triangle—90 degrees and the angle of the Fan Song's vertical beam—to calculate its hypotenuse.