Thanh Hoa Bridge

The Thanh Hoa Bridge, spanning the Song Ma river, is situated 3 miles (4.8 km) northeast of Thanh Hóa, the capital of Thanh Hoa Province in Vietnam. The Vietnamese gave it the nickname Ham Rong ( Dragon's jaw). In 1965 during the Vietnam war, it was the objective of many attacks by US Air Force and US Navy aircraft which would fail to destroy the bridge until 1972. In their first air combat, a small force of seemingly mismatched MiG-17s inflicted significant losses on much larger and more advanced American F-105 Thunderchief and F-8 Crusader fighters at a cost of 3 of their own, with an F-100 Super Sabre claiming the first probable American kill of the conflict. This would lead to significant changes in American tactics, training and fighter design, and a return to dogfighting in air combat doctrine. Eventually, in 1972, the bridge was destroyed by A-7 Corsair bombers using laser-guided bombs and conventional bombs.

The bridge
Originally built by the French during the colonial era in Vietnam, the Thanh Hoa bridge was sabotaged by the Viet Minh in 1945. From 1957, the Vietnamese started rebuilding it. It was a grey metallic construction, resting on a central concrete pier, and on concrete abutments at each extremity. Completed in 1964, and inaugurated by Ho Chi Minh himself, the final bridge was 540 feet (160 m) long, 56 feet (17 m) wide, and about 50 feet (15 m) above the river. Allowing the passage of both road and rail traffic, it was a vital link between different regions of North Vietnam, and when the war started, became a strategic passage for supplies and reinforcements sent to the Viet Cong fighting in South Vietnam.

Operation Rolling Thunder
With the beginning of Operation Rolling Thunder (the bombing campaign against strategic targets in North Vietnam), the decision was made in March 1965 to interdict the North Vietnamese rail system, including the Thanh Hóa bridge. The Vietnamese, realizing the importance of the bridge, had set up an impressive air defense network, five air defense regiments being stationed in the area. The first " and largest " strike package to be sent against the bridge was codenamed 9-Alpha. Led by Colonel Robinson Risner, it comprised 79 aircraft, including 46 F-105 Thunderchiefs as the main strike force. Other types were 21 F-100 Super Sabres as AAA suppressors, 14 F-100s acting as MiG CAP and two RF-101C Voodoos to do damage assessment, plus 10 KC-135 tanker aircraft. The F-100s were based in South Vietnam, while the others were based across Thailand. Flights of four F-105s from Koran and Takhli would be air refueled over the Mekong River, then cross Laos to just south of the bridge. The bombers would continue east until over the Gulf of Tonkin. Launched on April 3, 1965, the attack saw all strike aircraft deliver their payload. Sixteen of the F-105s carried a pair of Bullpup missiles, one under each outer wing pylon. This was an early combat use of early "smart" precision guided missiles that were guided by radio and joystick, requiring two passes to launch each of two missiles per plane before the evolution of laser-guided bombs which eventually felled the bridge late in the war. Capt. Bill Meyerholt observed as the missile streaked toward the bridge and made a good hit; when smoke cleared,there was no visible damage to the bridge. The tiny 250 lb warheads merely charred the massive structure. Crews grimly joked that Bullpups on the Dragon's Jaw were as effective as shooting BB pellets at a Sherman tank. The other F-105s each carried 3 tons of explosives in the form of eight 750 lb (340 kg) bombs, more than B-17s had delivered over targets like Berlin. The first wave of bombs drifted due to a strong southwest wind. The last flight, led by Cpt. Carlyle S. "Smitty" Harris, scored hits on the roadway and superstructure. After 32 Bullpups and 1200 bombs had decorated the bridge with numerous hits, charring every part, the bridge did not fall, though traffic was stopped for a few hours. This was the only result of the raid, which had cost two aircraft " one F-100 (Lt. George C. Smith flying flak suppression) and one RF-101 " shot down. Risner's Thunderchief was crippled by ground fire, but despite smoke in the cockpit, Risner continued to direct the strike before flying safely back to Da Nang. To meet the raid, the VPAF had sent out two flights of four MiG-17s from Noi Bai airbase at 9:47. The original plan was for the first flight to act as decoy. The second flight never reached the strike force, as flight leader Pham Ngoc Lan spotted F-8E Crusaders from the USS Hancock covering the operation. He dived to attack at about 1,000 feet, and fired at a range of 700 feet. His gun camera showed a blazing F-8 which he reported had crashed. At 10:15 wingman Lieutenant Phan Van Tuc fired on another F-8, claiming a second victory. Pilots Ho Van Quy and Tran Minh Phuong also opened fire on two F-8s, but were out of gun range. In the VPAF's evaluation, their success was due to proper preparation, using surprise and engaging only in close dogfights. While the US Navy records that all of the Crusaders returned, a plane flown by Lt. Cdr. Spence Thomas was so damaged it diverted to Da Nang and was written off as destroyed upon landing. That could make Lan's attack the first air-to-air kill not only by the VPAF's MiG-17s, but the first air victory of the conflict. The Navy recorded that an A-4 Skyhawk of Lt. Cdr. R. A. Vohden was lost to AAA; Vohden spent the rest of the war as a POW. The VPAF had nevertheless demonstrated the ability to engage US fighters, and afterwards recognized April 3 as Air Force's Day. On the American side, the failure to drop any spans led to a new attack scheduled for the next day; it was expected by VPAF commanders. This time, 80 planes were engaged, including 48 F-105s, carrying only 750 lb (340 kg) bombs, as the inadequacy of the Bullpup had been fully demonstrated. During the 4 April 1965 engagement, a tiny force of eight MiG-17s (half flying as decoys) from the 921st "Sao Dao" (Red Star) Fighter Regiment (FR) was again given the daunting task of confronting a massive armada of modern American supersonic fighter-bombers. The 46 F-105 Thunderchiefs were escorted by a flight of 21 F-100 Super Sabres from the 416th Tactical Fighter Squadron (TFS), 4 Sidewinder-armed for MiGCAP, and 17 armed with 2.75-inch HVAR to suppress AAA batteries. Each flight was given a call sign. These included "Steel," "Iron," "Copper," "Moon," "Carbon," "Zinc," "Argon," "Graphite," "Esso," "Mobil," "Shell," and "Petrol." "Cadillac" flight conducted Bomb Damage Assessment, while the search and rescue included A-1 Skyraiders, call sign "Sandy," and HH-3 Jolly Green Giant rescue helicopters, call sign "Jolly Green." The VPAF made AAA sites the first line of defence, with fighters attacking after ground gunners ceased fire. After taking off at about 10:20, the MiGs would break into decoy and attack flights. The leader was second-in-command Nguyen Van Tien, while Dao Ngo Ngu handled the ground control command. The Americans started with recon flights over Thanh Hoa. Then the attacking jets flew in flights of four. One flight would attack at a time while others circled awaiting their turn. Although, on paper, the F-105 was double supersonic, when loaded with ordnance under its wings, it was subsonic and unready to tangle with any fighters that might get past the escorts. Covering the north, in the direction of Hanoi's airfields, escorting F-100s sixty miles north of the Song Chu estuary where the river meets the sea, were to warn of enemy aircraft. and if possible to intercept, while 4 others orbited south of the estuary. The MiG attack came instead from the south, with part angling off toward the west, perhaps to draw away escorts as a decoy. As the MIGCAP F-100s flew south, they spotted MiG-17s flying in from the sea toward the F-105s, and radioed the warning: "Break off!" But their warnings weren't heeded due to garbled transmission. The strike aircraft flew on like sitting ducks, unaware of the incoming threat. While North Vietnam had full radar coverage and ground control of their pilots, the short-range, forward-scanning radars in the F-100s didn't spot the MiGs in a part of the sky where they were not expected. The USAF would later use EC-121s and develop the E-3 AWACS to provide full 360-degree radar coverage for strike packages. Coming from clouds above, the MiG-17s tore past the escorts and dove onto the bomb laden Thunderchiefs, Communist flight leader Tran Hanh spotted four F-105Ds at 10:30 starting to drop their bombs, ordering his wingman, Pham Giay, to cover his attack. He fired his 3 cannons at 400 meters, observing one F-105, piloted by Major Frank E. Bennett (355th TFW, KIA) fall in flames into the Gulf of Tonkin. The flight leader attempted to recover at Da Nang but had his controls freeze up within sight of the base. Ejecting, he was killed when his parachute failed to open before he struck the water and he drowned. As the Thuds turned to attack the MiGs, the MiG split into two groups on the north and south sides of the bridge. Supported by Tran Nguyen Nam, Le Minh Huan downed another F-105D, callsign Zinc 2 piloted by Capt. J.”‰A. Magnusson. He radioed that he was heading for the Gulf if he could maintain control of his aircraft. Magnusson's aircraft finally bailed out 20 miles away over the Gulf of Tonkin near the island of Hon Me, and was eventually listed as missing and then killed after a 48-hour search. The USAF confirmed the two F-105 losses during that engagement. The remaining fourth plane found himself in the sights of another MiG-17 who he could not shake. In desperation, he tried a snap roll which slowed his plane so that the MiG-17 over-shot him, as his captain had recommended. Finding himself on the MiG's tail, he was too surprised to attempt to shoot down the MiG with his gun. The fortunate survivor from Nellis was the legendary John Boyd who would be a significant voice in the design of America's future dogfighters. MiG-17 flight leader Tran Hanh was credited with one confirmed F-105 victory during that engagement. He stated that three of his accompanying MiG-17s had been shot down by F-105s. His own plane narrowly escaped through hard manoeuvring, but he lost contact with ground control. Short on fuel, he made a hard landing in the Ke Tam valley (Nghe An province) where he was detained by the locals until he showed his VPAF badge. Hanh probably confused the escorting F-100s for an F-105. As only one American pilot even claimed a probable kill, his other comrades more likely could have collided or been hit by their own AA fire. Nevertheless, in exchange for their significant sacrifice, the North Vietnamese MiG-17s had scored their first confirmed aerial victories in jet-to-jet combat. After the quick success of downing two American fighters, the outnumbered North Vietnamese defenders faced a sky full of the remaining angered f-105s and F-100s now fully alerted to their presence. Three F-100s from the MiGCAP, piloted by LTC Emmett L. Hays, CPT Keith B. Connolly, and CPT Donald W. Kilgus, all from the 416th TFS, engaged the MiG-17s. As the F-100s closed in, they hesitated to fire missiles which might hit their F-105s. The lead F-100 fired an air-to-air missile when it had a clear shot, but it passed above its target, while Connolly and Kilgus engaged with 20mm cannon. Only Kilgus claimed and was credited with a probable kill, while it was assumed the other MiGs escaped. Based upon the report, the F-100s had obtained the first US aerial combat victories during the Vietnam War, and if confirmed, would be the only air-to-air MiG kill by an F-100 during the conflict. North Vietnamese ground was credited with downing "Sandy" A-1H Skyraider, killing Capt. Walter Draeger, and also the F-105 of Capt. Carlyle "Smitty" Harris, who survived and became one of the earliest American prisoners of war. On 15 April 1965, a communist publication interviewed a MiG pilot who had actually shot down Capt. Harris' F-105 rather than ground fire. Harris was classified MIA, but had been actually imprisoned in Hanoi until 1973, when fellow POWs credited Capt. Harris with introducing the " tap code" into the prison system. In North Vietnam, MiG-17 flight leader Tran Hanh became a national hero. What in retrospect might seem to be tactical draw after losing all of their defending fighters and three pilots, and viewed by other Americans as an unprovoked aggression against civilian targets, was celebrated as a "glorious victory over US aircraft to ensure the flow of war supplies to the south". For their part, anti-aircraft gunners received the Victory Order and the Military Exploit Order. On the 45th anniversary of the battle in 2010, Vietnam celebrated the downing of 47 US aircraft over the two days of the 454 sorties over two days that dropped 350 bombs on and around the bridge, calling it "the symbol of the Vietnamese people's will to defend their country...the Great Spring Victory to liberate the South and reunify the country." The raid had been carried out with great precision, but despite having been hit by more than 300 bombs, the Thanh Hoa bridge still stood. As minor damage caused the circulation to be interrupted for a few days, it was seen as a modest success cost that had cost the US Air Force three F-105s. But U.S. Air Force chief of staff General John P. McConnell, was "hopping mad" to hear that two of America's most advanced F-105 Thunderchiefs had been shot down by slow, elderly left-over MIGs of the tiny 36-jet North Vietnamese air force. The subsonic MiG-17s had been in service for over 12 years since 1953, and was barely improved over the original MiG-15s that sparred with F-86 Sabres in dogfights over the Yalu River. By contrast, the F-105 was two generations ahead (and the escorting F-100s one generation ahead) as the USAF's most advanced Mach 2 class fighter bomber with sophisticated navigation and radar systems which could be armed with sidewinder missiles and a bombload comparable to WWII bombers. But at slower speeds, the older MiG could out-manoeuvre any of its adversaries, and at a time when air-to-air missiles highly unlikely to actually destroy their targets, the cannons of the MiG were much more reliable, and deadly against F-105s which at the time were vulnerable to hits on systems such as hydraulics. The losses to MiGs resulted in the subsequent replacement of the F-100 Super Sabre escorts with F-4 Phantoms. The incident would start a series of events that would lead to a reassessment of fighters better suited to close-in dogfighting. While the F-105 would finish off its service with a slightly better than even kill to loss ratio over MiGs, the large plane had been designed primarily to deliver bombs at low level rather than shoot down other fighters. Its replacement was the even larger Phantom which had been designed to fire missiles at stand-off ranges rather than a turning dogfight. This experience would re-introduce the requirement that future fighters would need to be able to mix with MiGs on more equal terms and not just shoot missiles from a distance. This would lead to training programs such as Top Gun and development of the F-14 Tomcat. Along with the F-15 Eagle and other teen-series fighters, the new fighters that came on line during the 1970s would dominate American airpower for the remainder of the twentieth century.

US Navy attacks
With the establishment of the Route Package system, the Thanh Hoa area was allocated to the US Navy. Between 1965 and 1968, until US President Lyndon B. Johnson temporarily called off air raids against North Vietnam, the bridge was a regular objective for navy Alpha strikes. Different types of aircraft were engaged including A-3 Skywarriors, A-4 Skyhawks, A-6 Intruders, F-4 Phantoms and F-8 Crusaders. Several types of weapons were launched at the bridge including AGM-62 Walleye missiles, but none had the precision and power to destroy it permanently. Several times, traffic over the bridge was interrupted, but every time, the North Vietnamese dutifully repaired the damage.

Operation Carolina Moon
In May 1966, an innovative attack, Operation Carolina Moon, was planned by the US Air Force. A new weapon was to be used: a large magnetic mine, that implemented a new energy mass-focusing concept. The plan was to float the mines down the river, till they reached the bridge, where the magnetic sensors would set off the charges, hopefully wrecking it permanently. The only aircraft with a large enough hold to carry these weapons was the slow-flying C-130 Hercules transport, so the operation was due to take place at night, to reduce its vulnerability. On the night of May 30, a first Hercules dropped 5 mines. A North Vietnamese prisoner later revealed that 4 of the 5 mines had in fact exploded under the bridge, but not caused any significant damage. However at the time the Americans did not know this, as after-mission reconnaissance had showed the bridge still standing, and a second raid was planned, with a different crew, for the following night. This second attempt turned to disaster: the Hercules was hit during its low-level run and crashed, killing the entire crew. An F-4 engaged in a diversionary attack nearby was also brought down and its crew lost.

The final blow
Between 1968 and 1972, bombing of North Vietnam was discontinued, enabling the North Vietnamese to repair their infrastructures, including the Thanh Hoa bridge. With the communist invasion of South Vietnam in 1972, a new bombing campaign was instituted: Operation Linebacker. On 27 April, 12 Phantoms of the 8th Tactical Fighter Wing, based at Ubon, Thailand attacked the Thanh Hoa bridge. 8 of their number carried laser-guided bombs. The raid was carried out without hitch, and when the dust of the explosions had cleared, it became apparent that the bridge had been dislodged from its western abutment, dropping one half into the river. To complete its destruction, a second attack was scheduled for the 13 of May when 14 Phantoms were engaged, with LGBs of up to 2,000 lb (910 kg) aimed at the central pillar supporting the bridge. Once again the attack was successful and the "Dragon's jaw" was rendered completely unusable. The US command, however, was not satisfied, and ordered a final attack on the 6th of October. This time, four U.S. Navy A-7s from VA-82, aboard USS America, successfully delivered 8,000 lbs of high explosives with two planes carrying two 2,000 lb (910 kg) Walleyes, while two other carried also 2,000 lbs in Mk 84 GP bombs. In a simultaneously attack, the centre pilling on the bridge's west side was hit and broke the span in a half. After this, the Thanh Hoa bridge was considered permanently destroyed and removed from the target list.

Aftermath and losses
The North Vietnamese made various fanciful claims as to how many planes they shot down, but the US recognizes the loss of only 11 aircraft during attacks against the bridge. However, the concentration of air defense assets also took its toll on passing aircraft and in total an estimated 104 American pilots were shot down over a 75-square-mile (190 km 2) area around the bridge during the war. 873 air sorties were expended against the bridge and it was hit by hundreds of bombs and missiles before being finally destroyed. It became something of a symbol of resistance for the North Vietnamese, and various legends of invincibility were attached to it. For the US planners, it became an obsession, and many raids were planned against it, despite their unpopularity with the pilots. A cynical rewording of the song the " Red River Valley" was sung by fighter pilots, referring to this dangerous target. In his 1976 essay collection, Mauve Gloves & Madmen, Clutter and Vine, Tom Wolfe recounted a rueful story that circulated among Navy pilots who flew sorties against the Thanh Hoa Bridge. In their telling, the Earth consisted of two hemispheres, spring-loaded and held together opposite the hinge by the bridge. When it was destroyed, the story went, the two hemispheres would fly apart, flinging humanity into space. While the first employment of the Bullpup in 1965 proved a disappointment, the ultimate destruction of the bridge finally proved the promise and effectiveness of precision-guided munitions, opening the way to a new era of aerial warfare. The 1965 strikes were the first employment of modern strike packages which were combined and launched against that specific target, leading up to an evolution of air warfare to 1972 which was employed very effectively with minimal losses in Desert Storm. The shock of losses of modern fighters in dogfights in 1965 was a landmark which led to a major shift in fighter design away from missile firing interceptors to agile designs capable in short-range air combat.

Belligerents United States North Vietnam Casualties and losses 11 aircraft destroyed 3 MiG-17 (1965)
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