It was difficult to land a direct shot at a target that was only 15 feet wide from a medium altitude. Experience taught us that even close calls would not significantly harm a bridge with sturdy construction
The sole American medium bomber to fly in the China-Burma-India (CBI) Theatre was the B-25 Mitchell. Starting operations in India and China, respectively, in July 1942, until the conclusion of the war, the B-25 was continuously in the air. One medium bomber group was assigned to each of the Tenth and Fourteenth Air Forces, while the Fourteenth Air Force also had a medium bomber group in the Chinese American Composite Wing (CACW). The Mitchell was flown by the B-25 units in the CBI Theatre, who employed the plane for a variety of missions.
The Fourteenth Air Force’s medium bomber units switched to low-level strafing of land, transportation, and shipping targets as aerial opposition decreased during the course of the B-25 operations in China.
The 341st BG launched a campaign against road and rail bridges in southern China and French Indochina in 1945 by employing the low-level bridge-busting strategies used by the B-25 squadrons deployed in India.
Getting a direct shot on a target that was only 15 feet wide from a medium altitude was difficult, as Edward M. Young explains in his book B-25 Mitchell Units of the CBI. Experience taught us that even close calls would not significantly harm a bridge with sturdy construction. The problem was made worse by the fact that Imperial Japanese Army (IJA) engineers were able to create bypass bridges next to destroyed structures in addition to performing quick repairs to even the worst damage.
For instance, the Myitnge bridge was the target of 39 sorties by the B-25s and B-24s of the 7th BG, during which the Liberators dropped 1219 bombs and scored 18 hits. This indicated that only 1.5% of all dropped bombs actually hit their intended target. The average for the medium bombers was better, with one hit occurring every 15 missions. The bombers tried 500-, 1000-, and even 2000-lb bombs, but the results were much the same.
17 percent of all the bombs landed on Burma by the USAAF in 1943 were directed toward the country’s railway system’s six main bridges, although the campaign was largely ineffective. A bridge could only be seriously damaged by a direct hit, and using the techniques used, the chances of doing so were statistically next to zero.
The members of the 490th BS understood they were in charge of carrying out the bridge-busting campaign in Burma since their squadrons were headed for China. Lt Col Robert McCarten, the squadron commander, was confident that the team would solve the issue. The 490th made an effort to create strategies that would be effective in the final months of 1943. After failing to bomb from medium altitudes, the unit shifted to low-level strikes, employing skip bombing techniques pioneered in the Pacific. However, once dropped, the bombs frequently bounced over or under a bridge to explode beyond, causing little damage at all. A failed effort to dive-bomb the B-25 only served to highlight how unprepared it was for such an assault.
Ironically, on January 1, 1944, a glide-skip (GLIP) bombing was the only way to solve the problem. One of the six crucial bridges in Burma’s railway system, the Mu River bridge, was to be bombed that day by squadron operations officer Capt. Robert Erdin. He made the decision to take a new approach to the target. Before delivering their bombs, the B-25s flew at a diagonal or right angle to the bridge in the majority of attacks. Before launching his bombs, Erdin decided to follow the line directly to the bridge.
Coming in at a low level, he was abruptly compelled to lift up just before launching his explosives in order to avoid a large dead tree that was directly in front of him. Erdin quickly pushed his B-25 down one more and then hit the bomb release button, fully anticipating seeing his bombs bounce off the bridge. Two of the bridge’s spans collapsed into the river, stunning him and his team. His bombs were dropped in a slight descent, and because of the angle at which they landed, instead of bouncing off the bridge, they struck it and quickly exploded. This method turned out to be the solution. The 490th BS would set an astounding destruction record in the months to come with some improvements and further training.
B-25 Mitchell Units of the CBI is published by Osprey Publishing and is available to order here.
Photo by U.S. Army Air Forces, Air Force Historical Research Agency, and NARA