Devoured by the Dragon

The men came bursting into the briefing room at Danang Air Base, whooping and hollering. Obviously, they had had a successful mission. It was a warm early summer night in Danang, South Vietnam, and I was on duty as an Air Intelligence Officer. Part of my job was to debrief aircrews after their missions, and this one was unusual.

Their mission was almost unbelievable: attack a heavily North Vietnamese-defended bridge with parachute-retarded floating mines dropped from a slow, unarmed C-130 cargo plane.

In a war, bridges are a vital link in the transportation network. Blowing them up delays the movement of men and supplies. During the Vietnam War, the bombing campaign against North Vietnam struck many types of targets – ports, fuel oil facilities, roadways, and, of course, bridges. 

One of the key bridges spanning the Song Ma  River is located on the southeastern coast of North Vietnam, about three miles northeast of the city of Thanh Hoa and about 70 miles south of Hanoi. The bridge was a crucial link to the south for truck and rail traffic. The Vietnamese even gave a nickname to the Thanh Hoa Bridge – "Ham Rong" (Dragon's Jaw). 

The Thanh Hoa Bridge was no average target. At 540 feet in length, it is the longest single-span bridge in Vietnam. It is a combination rail and highway bridge, 56 feet wide, with the railway in the center and two 10-foot wide roads on either side. It rises to a height of 50 feet above the river and consists of two steel spans resting on a massive reinforced concrete pillar over 50 feet in circumference. After the first attempted strikes, the North Vietnamese gradually added eight additional concrete pillars at the ends of the bridge. This made the Thanh Hoa Bridge an exceedingly challenging target for 1960s weapons. 

Not only was the target well-built, but it was also well-fortified. The Thanh Hoa Bridge was perhaps the most heavily defended target in North Vietnam, surrounded by hundreds of anti-aircraft guns, ranging in caliber from 12.7 to 85 millimeters,  plus surface-to-air-missiles.

Despite numerous previous attacks using conventional bombs, the bridge remained open. Even when it was damaged, the damage was quickly repaired. The bridge became a symbol of resistance against the North Vietnamese. U.S. Air Force and Navy aircraft – principally F-105s, F-4s, and A-7s – used conventional and laser-guided bombs, but the 500- and 750-pound bombs typically used could not inflict lasting damage. It was a source of frustration for U.S. Air Force and Navy aviators who made hundreds of attacks on it.

Out of this frustration grew an unconventional plan: a massive floating mine would be dropped into the Song Ma River away from ground defenses. It would detonate when it floated into contact with the bridge. The mine weighed more than a ton and a half and had a maximum width of eight feet. It had two fuses, a focused warhead that would direct the blast and would be dropped from a cargo plane, using two 64-foot parachutes to slow its fall.

The plan was to drop several mines upstream to avoid anti-aircraft fire and let them float down the river until they reached the bridge, where the magnetic sensors would set off the charges. This would, it was hoped, wreck the bridge permanently. The only aircraft large enough to carry these weapons was the slow-flying C-130 Hercules transport. This meant the mission had to be flown at night to reduce its vulnerability. 

In early April 1966, the Air Warfare Center published OPLAN 155, known as "Carolina Moon." This called for two crews from the 61st Troop Carrier Squadron at Sewart AFB, Tennessee, using two C-130E aircraft, one primary and one alternate. Between mid-April and mid-May, the two crews trained at Eglin Air Force Base, Florida, practicing how to drop the weapons. 

One crew was led by Maj. Richard T. Remers and the second by Maj. Thomas F. Case. Various technicians and specialists took part in examining how to drop the weapon, what parachutes to use, and how to ensure the weapon would navigate the river.

In mid-May, the two aircraft and their crews deployed to Danang Air Base, South Vietnam. They received additional target information and took part in selecting the final mission profile. Ten of the large weapons were available, enough for two missions. Final orders were set for late May 1966 for the first mission.

They were courageous, these airmen. At least some of them must have had their doubts about how practical this mission was and how unlikely success would be. Even the Tactical Air Warfare Center worried the mines would get stuck in the river bank before getting to the bridge and "concluded that the chances of success were small," according to an official summary. "Alternative proposals apparently offered a lesser chance of success," the same report added.

The first mission was flown on the night of  May 29-30, 1966. Both aircraft took off, with the second acting as an airborne spare. Just after midnight on May 30, Major Remers took off from Danang, flying just 100 feet over the water of the South China Sea until reaching his entry point on the coast of North Vietnam. In less than an hour, he was over land heading up the Song Ma, under the guidance of two navigators, Capt. Norman G. Clanton and 1st Lt. William R. Edmondson. After the first aircraft reached the mouth of the Song Ma River, the second aircraft was recalled. 

The C-130 flew at about 100 feet above ground toward the target, aiming for a release point about two and a quarter miles short of the bridge. The mission plan included an option that if the anti-aircraft fire was light, the aircraft could continue another 5,000 feet, releasing the weapon about 7,000 feet short of the bridge span. The plane received light fire and proceeded to the 7,000-foot release point. Flying about 150 miles per hour, the plane popped up to 400 feet for 30 seconds prior to release and dropped five mines. Heavy ground fire began just before the drop, but the plane then dropped to its previous low altitude and returned to Danang without incident. 

At the same time, a flight of four F-4C aircraft were carrying out a diversionary strike 15 miles south of the bridge. There were reports of heavy anti-aircraft fire in the vicinity of the bridge.

When the crew returned to Danang, they were jubilant. In the operations room, they talked about how they had dropped the mines and avoided ground fire. There was a sense of relief and accomplishment and bravado that only comes from tackling a seemingly impossible task and coming through it alive.

Unfortunately, the success was only apparent. The bomb damage assessment showed no damage to the bridge.

The drop had, in fact, succeeded to the degree that five weapons had been dropped and had floated down the river and exploded against the footings of the bridge. A North Vietnamese prisoner, a torpedo boat crewman, later reported that four of the five mines had, in fact, exploded under the bridge but had not caused any significant damage. The Air Force did not know this, as the bridge was still standing. So a second raid with a different crew was planned for the following night. That one was a disaster.

The second mission was set for 1 a.m. takeoff on May 31. In one of the ironies of the operation, Major Case asked that 1st Lt. Edmonson join his crew since he had experience from the first mission. It was a fateful decision.

The C-130E, call sign "Radium 1," flew below 500 feet to evade radar along the 43-mile route. The plane would rendezvous with a flight of F-4Cs that were assigned to the same mission. Weather conditions in the Thanh Hoa area included a few thin scattered clouds with moonlight. Visibility was seven miles. Approaching the target would expose the aircraft to enemy fire for about 17 minutes.

The ingress route was changed slightly from the first mission, but the final approach was the same. The same precautionary measures were taken – diversionary attacks and electronic countermeasures. The second Hercules was apparently hit during its low-level approach and crashed, killing the entire crew. An F-4C engaged in a diversionary attack nearby was also lost to ground fire. Pilots in the diversionary strike reported seeing heavy anti-aircraft fire in the vicinity of the bridge around the scheduled drop time, followed by a large ground flash. It appeared the C-130E reached the target area and was shot down.  

The next morning's reconnaissance mission revealed no damage to the bridge or any evidence of survivors. An extensive search was conducted, but nothing that could be positively identified as belonging to Case's C-130 was found. 

With this tragic finale, Operation Carolina Moon concluded, and its remaining personnel returned to the U. S. This unconventional tactic had not been successful. Many years passed before the remains of several of the missing Carolina Moon crew members were recovered. 

In 1986, the remains of Major Case, 1st Lt. Armon D. Shingledecker, 1st Lt. Harold J. Zook, and A1C Elroy E. Harworth were returned to the United States for burial. In 1998, the remains of A1C Phillip J. Stickney were returned. 

The other Carolina Moon C-130 crew members, Lt. Edmondson, Capt. Emmett R. McDonald and SSgt. Bobby J. Alberton are still listed as missing in action but are presumed dead. 

After seven years, nearly 900 sorties, 11 lost aircraft, and a great expenditure in lives and munitions, the Dragon's Jaw was finally broken, but only temporarily. In a series of attacks in 1972, with the introduction of new technology in the form of precision electro-optical and laser-guided bombs, U.S. air power, at last, succeeded in destroying the Thanh Hoa Bridge. 

The bridge was restored in 1973 and continues to stand. 

An unconventional warfare tactic failed, but the men who attempted it deserve to be remembered. In spite of the odds against success, these airmen showed the courage and professionalism that honors all who serve. 

The author was a U.S. Air Force air intelligence officer at Danang Air Base at the time of the "Carolina Moon" mission.