Week of April 7

Week of April 7

On April 3, 1965, as part of Operation ROLLING THUNDER, the U.S. Air Force launched a strike against the Thanh Hóa Bridge. A combination rail and highway bridge, it spanned the Sông Mã (Ma River) in North Vietnam, approximately 70 miles south of Hà Nội. The Thanh Hóa Bridge was a crucial choke point along one of the most important North Vietnamese supply routes funneling truck convoy and railroad traffic to the South. It was 540 feet long, 56 feet wide, and rose to a height of 50 feet above the Sông Mã (Ma River). The bridge consisted of two steel spans resting on a massive reinforced concrete pillar over 50 feet in circumference. The mission to destroy it became one of the most frustrating efforts of the war for Air Force and Naval aviators.

In all, 79 U.S. aircraft—primarily F-105 Thunderchief fighter-bombers, A-4 Skyhawk attack aircraft, and F-4 Phantom fighters—attacked the bridge on April 3 with rockets and bombs. Due to the technological limitations of 1965 unguided “dummy” munitions, however, few of the U.S. aircraft were able to score a direct hit on the bridge. The few weapons that did hit the bridge were radio-guided AGM-12 “Bullpup” missiles, which bounced off the bridge’s steel and concrete structure almost harmlessly. As one Air Force historian puts it, “it became all too obvious that firing Bullpups at the [Thanh Hóa Bridge] was about as effective as shooting B-B pellets at a Sherman tank.” Even with heavier weapons, hitting a 56-foot wide target while moving at 500 miles per hour through heavy antiaircraft fire and surface-to-air missiles proved an incredibly difficult task.

After the initial strike attempts, the North Vietnamese gradually added eight additional concrete pillars at the ends of the bridge. Combined with the steep hills on either side of the span, this made the Thanh Hóa Bridge an exceedingly challenging target for 1960s weaponry.

The U.S. Air Force and Navy launched numerous strikes against the Thanh Hóa Bridge over the next three years, attacking it with thousands of tons of ordnance before a general bombing halt was ordered by President Lyndon B. Johnson, in 1968. According to one Navy official, the area around the bridge “look[ed] like a valley on the Moon.” None of these strikes ever managed to down even one of the bridge’s spans or to take it out of service for any significant amount of time. North Vietnamese repair crews worked swiftly to repair damages.

Finally, in May 1972, with the introduction of brand new technology in the form of precision electro-optical and laser-guided bombs, U.S. airpower at last succeeded in destroying the Thanh Hóa Bridge. This eventual success highlights the importance of the research and effort that went into the development of precision-guided weaponry during the Vietnam War—technology that served as the foundation for the extremely accurate GPS and laser-guided ordnance used by the U.S. military today. 1

1A.J.C. Lavalle, ed., The Tale of Two Bridges and The Battle for the Skies over North Vietnam (Washington, D.C.: Office of Air Force History, 1985), 3, 6, 9, 31, 36–38, 78–79, 85–86 (quotes on pp. 36, 46); Jacob Van Staaveren, Gradual Failure: The Air War Over North Vietnam, 1965–1966 (Washington, D.C.: Air Force History and Museums Program, 2002), 105–7; Ronald Bruce Frankum, Like Rolling Thunder: The Air War in Vietnam, 1964–1975 (Lanham, Md.: Rowman and Littlefield Publishers, 2005), 22, 32, 157–58.