Thud Ridge: how a nuclear bomber became the workhorse of Rolling Thunder

The Republic F-105 Thunderchief was never meant to do what it became famous for. Designed in the early 1950s as a single-seat, single-engine strike fighter, its job was to carry one nuclear weapon in an internal bay, low and fast, to a target in Eastern Europe. Everything about the airframe followed from that: the swept wing with forward-hinged intakes, the enormous Pratt & Whitney J75, the fuselage bay that was later plated over and filled with fuel.

The ridge

Pilots inbound to the Hanoi area from Thailand learned to fly the long, north-west-to-south-east ridgeline that pointed at the capital like a gunsight. They called it Thud Ridge. It gave a hard navigation reference, some terrain masking from the radars in the valley, and a landmark to run back to when things went wrong. Jack Broughton's 1969 memoir made the name permanent, and gave the aircraft its identity: not the sleekest, not the most agile, but the one that went downtown day after day.

You could go faster in a Thud on the deck than anything else in the war, and you often needed to.

Why the losses were so heavy

The F-105 flew most of the Air Force's strike sorties against North Vietnam in the Rolling Thunder years. The targets — bridges, rail yards, the Thai Nguyen steel works — sat inside the densest integrated air defence anyone had yet attacked: radar-directed anti-aircraft artillery, SA-2 Guideline missiles, and MiG-17s and MiG-21s vectored from the ground. The tactics of 1965 asked a big, fast, non-manoeuvrable aircraft to fly predictable routes at medium altitude into that. Losses were, by any modern standard, unsustainable: several hundred of the roughly 800 airframes built were lost in Southeast Asia, the great majority to ground fire rather than fighters.

What the Thud left behind

Two things. First, the Wild Weasel mission. Two-seat F-105Fs and the later G models, fitted with radar-homing receivers and Shrike and Standard ARM missiles, went in ahead of the strike package to find and hit the SA-2 sites. The doctrine — first in, last out, "YGBSM" — is the direct ancestor of every SEAD unit since.

Second, an argument about aircraft design that has never stopped. The F-105's failure was not the aircraft; it was the mismatch between a platform built for one war and the war it was sent to fight. The next generation — the F-4 in the near term, the F-15 and F-16 later — was shaped by that lesson as much as by any threat study.

Today the Thunderchief is a museum piece and a call-sign. But the shape of the problem it exposed — a heavy, expensive platform sent repeatedly against a maturing defence — is the shape of a lot of current debates about air power, and about the survivability of everything from tankers to merchant ships. Which is why it opens this journal.