Called the "Dragon's Jaw" (Ham Rung) by the Vietnamese, this bridge was bombed more than any other target in North Vietnam. It was bombed so often because it refused to go down. Fighter-bombers dropping iron bombs failed to even damage the bridge. Thanh Hoa Bridge
At 5,532 feet in length, it was the longest single-span bridge in North Vietnam (the Doumer Bridge in Hanoi was longer but not a single span). It was a 38-foot wide, combined highway and railway bridge. The railway occupied the center of the bridge, with two 10-foot wide roads on either side.
This bridge replaced the original French-built bridge which was destroyed by the Viet Minh in 1945. The Chinese provided technicians who rebuilt the bridge which spanned the swift flowing Song Ma. Although work started in 1957, the bridge was not completed until 1964. Ho Chi Minh presided over the dedication of the bridge.
The first attack on the bridge occurred on 3 April, 1965. 120 750lb bombs and thirty-two Bullpup missiles were expended on the target. There were numerous direct hits with Bullpups but they barely charred the paint on the massively over-engineered structure. Several 750lb bombs hit the roadway and superstructure of the bridge but did no damage.
It was clear that even when the fighter-bombers were able to score a direct hit on the bridge, a 750lb bomb was simply not powerful enough to drop a span. The Air Force tried using C-130 cargo aircraft to drop special 5,000lb "mines" into the Song Ma above the bridge the intent being for the mines to float down stream under the bridge, detonate, and destroy or at least severely damage the structure. Two attacks were carried out, with neither being effective and with the loss of a C-130 during the second attack. No more C-130s were employed.
Although the bridge was hit numerous times, the NVA were always able to get it back into service rather quickly. Attacks would continue without success until the bombing halt of November 1968. The next attack would not occur until May, 1972 during Operation Linebacker I.
On 13 May 1972, 14 U.S. Air Force F-4 Phantoms headed for the Dragon's Jaw. They were carrying nine 3,000lb Laser Guided Bombs (LGB), fifteen 2,000lb LGBs, and forty-eight conventional 500lb pounds. After they had dropped their bombs the western span had been dropped, knocked completely off of its 40-foot concrete abutment. The bridge superstructure was also heavily damaged as were the bridge approaches meaning that the bridge would be out of action for quite some time. DOD Photos.