A B-26C Invader on a bombing run over Korea.
USAF light bombers destroyed this railroad bridge north of Pyongyang, North Korea.
The Rail Interdiction Program, as an estimate of August 14, 1951, explained, called for fighter-bombers to attack rail lines throughout North Korea. The Fifth Air Force estimated that using only its own aircraft it could destroy the entire system in six to eight months. But to reduce the period to ninety days, the Air Force called on the Navy to assume responsibility for interdicting the lateral line between Samdong-ni and Kowon, and the east coast line from Hungnam through Wonsan to P’yonggang. The plan also designated five bridge complexes as targets. Bomber Command, however, would assume responsibility for the destruction of only four-those at P’yongyang, Sonchon, Sunch’on, and Sinanju. It declined to attack the bridges at Huich’on because of their proximity to Manchuria-and the bases of the MiGs. The Eighth Army, for its part, agreed to limit its requests for close air support to ninety-six sorties a day in order to free aircraft for interdiction. The Fifth Air Force set about its task confidently. The estimate of August 14 stated that the objective was to render the enemy incapable of “opposing the U. S. Eighth Army effectively,” should the United Nations resume the offensive. In November, one of Vandenberg’s briefers ventured the prediction that interdiction alone would compel the enemy to retire from the 38th Parallel to a line “generally from P’yongyang through Kowon. . .” This was a much more ambitious purpose than those of the previous interdiction campaigns, the object of which had simply been to prevent the enemy from taking the offensive. The reasons for this assurance are not readily apparent, given that the two previous interdiction plans had undeniably failed. Part of the confidence was perhaps due to the fact that by the time the Rail Interdiction Plan began on August 19, the Fifth Air Force had finally succeeded in moving all its fighter-bomber wings to Korean bases from Japan.
The initiation of the Rail Interdiction Plan caught the Chinese by surprise and initially unprepared to deal with a systematic assault on their rail system, different from earlier onslaughts. The night intruders reported that they had never before seen so many vehicles, many lighted, as convoys struggled to redress the diminished capacity of the railroads. A record number of vehicles for the war, 4,000, was counted on the night of August 26. While the Navy harried the east coast line between Hamhung and P’yonggang, the Fifth Air Force fought to close the western coastal line between Sonchon and Sariwon. If these two stretches could be kept inoperable, crucial transverse lines in the vicinity of P’yongyang would be useless. Each fighter wing was assigned a specific section of the line, fifteen to thirty miles in length. The attacks coincided with Sabre sweeps designed to draw the MiGs away from the fighter-bombers. Wing commanders enjoyed considerable latitude in planning their raids. Most used “group gaggles” of thirty-two to sixty-four aircraft, which broke away in small flights to bomb tracks with either 1,000-pound bombs or, more commonly, two 500-pound bombs. The attackers employed both glide-bombing and dive-bombing. The former, which entailed a long approach parallel to the ground, was favored for its accuracy. But where flak was heavy, dive-bombing was necessary to reduce a plane’s exposure to it. Comparing pilots’ claims against evidence from photographic reconnaissance, the Fifth Air Force’s Operations Analysis Office found that claims exceeded confirmed cuts by 220 percent. But nearly 13 percent of all bombs dropped severed track in the early stages of the Rail Interdiction Program, and nearly a quarter of all sorties resulted in cuts. During World War II, IX Tactical Air Command had managed to cut tracks only once for each eight or nine sorties. Following the bombing, the gaggles of fighter-bombers broke up into flights for armed reconnaissance. This practice, however, was markedly less effective than it had been formerly, for the enemy’s flak now forced the searching element to fly at about 3,000 feet.
Throughout the Rail Interdiction Program, the night intruders, flying an average of about sixty sorties nightly, claimed the lion’s share of vehicles. One wing of B-26s, based at Kunsan, was responsible for roads in western North Korea, while the other, flying from Pusan, covered the roads in the other half of the country. It became increasingly common to dispatch the Invaders singly so that all the major routes could be covered at least once during the night. This became increasingly feasible during the Rail Interdiction Program. The intruders turned increasingly from strafing to bombing, and bombardiers in the glass-nosed B-26Cs believed that they could dispense with the illumination that an accompanying aircraft would otherwise have had to provide. The B-26s carried proximity-fuzed 500- and 260-pound fragmentation bombs. A common load was four of the former and fourteen of the latter.
It appears that the chief reason for the increased resort to bombing was that most of the B-26s sent to Korea as replacements were Model Cs rather than the “hard-nose” Model Bs. The latter, with guns rather than glazing in the nose, had been specifically designed as strafers, and for that reason sent first to Korea. Whatever the reason for it, the change soon seemed vindicated by the claims of the night intruders. In July, they had claimed to have destroyed 750 vehicles and to have damaged 1,550. In August the figures shot up to 1,935 and 3,633, respectively. On the night of August 24 alone the B-26s claimed to have destroyed or damaged nearly 800 vehicles. These numbers invited skepticism. The Fifth Air Force, accordingly, ruled in September that a vehicle must be seen to burn or to explode before it could be claimed as a kill. But in October the intruders went on to claim the destruction of 6,761 trucks. Claims for November and December were, respectively, 4371 and 4,290.
The claims of the night intruders were almost always unverifiable because pilots rarely had anything like an exact idea of where they had executed an attack, and the Fifth Air Force, perennially short of reconnaissance aircraft, could not afford random searches for destroyed vehicles. The claims of the fighter-bombers, on the other hand, were comparatively easy to assess with photography. If exaggerated, they were nonetheless impressive. From Sinuiju south, the western coastal line was double tracked. By cannibalizing one line to repair the other, the enemy was at first able to keep the route open until repeated attacks had devastated long stretches of roadbed. During the first month of the Rail Interdiction Program, 70 percent of the coastal line between Sinuiju and Sinanju was reduced to a single track; for the stretch between Sinanju and P’yongyang the figure was 90 percent, and from P’yongyang to Sariwon it was 40 percent.
During the second month of the campaign, the interdictors began to destroy trackage faster than the enemy, who had exploited most of his opportunities for easy repairs, could replace it. The western coastal line was abandoned between P’yongyang and Sariwon after October 2. The segment Sinanju to Sukch’on went out of service about October 25, and only through the greatest exertions could the Communists keep open the stretch between Sinuiju and P’yongyang. The same was true of the central line from Huich’on through Sunch’on to Yangdok. By mid-November the interdictors had pulled still farther ahead: All the direct routes from Manchuria to the enemy’s major railheads at Yangdok and Samdung had been severed. They could still be reached, but only circuitously, by using the western coast route to Sinanju, taking the lateral line to Kunu-ri, and then traveling south through Sunch’on. It was also possible to travel down the central route from Kanggye to Kunu-ri, and thence through Sunch’on to the railheads. Both routes were uncertain, however, as Bomber Command was intermittently able to put the bridge at Sunch’on out of service. Notwithstanding their primary mission of defeating the second phase of the enemy’s push to extend his airfields, the B-29s also managed to reduce the serviceability of the bridges at P’ yongyang, Sinanju, and Sonchon. As the Navy had succeeded in keeping the eastern coastal line between Kilchu and Wonsan closed, the severing of the single short segment of line between Kunu-ri and Sunch’on would stop all through traffic between Manchuria and the central Korean railheads.
In mid-November victory seemed within the Fifth Air Force’s grasp. It was then that General Vandenberg heard the prediction that the Chinese and North Koreans would be forced to retire from the 38th Parallel. But scarcely had these confident words been uttered, the enemy’s countermeasures began to turn the tide of battle. There had been hints of this as early as September. Throughout the Rail Interdiction Program the Communists continued the increase of antiaircraft weaponry begun earlier in the year. The number of automatic weapons, very effective against low-flying fighter-bombers, grew particularly rapidly. Losses mounted quickly, soon surpassing once again the rate at which aircraft could be replaced; repair crews were first overworked and then swamped as they struggled to return damaged aircraft to service. In August, the Fifth Air Force lost 30 craft; another 24 were damaged. In September, 33 were lost and 233 damaged; in October, the figures were 33 and 239, and in November, 24 and 255.56 By October the fighter-bombers were being forced to expend 20 percent of their effort in largely unsuccessful efforts to suppress flak. They were also forced, moreover, to use dive-bombing almost to the exclusion of glide-bombing in order to reduce the danger from the enemy’s spreading flak, with the result that the effectiveness of their bombing decreased accordingly. By December, only 7 percent of their bombs were cutting tracks.
The halving of the fighter-bombers’ accuracy was serious. But there was worse: Fewer aircraft were finding the opportunity to bomb the railroads. The introduction of drop-tanks steadily expanded the MiGs’ area of operations. October found them as far south as P’yongyang. A “train” of sixty to eighty Chinese jets would fly into Korea at an altitude of 35,000 feet. As the force flew down the center of the peninsula, sections peeled off to battle the patrolling Sabres, while the main body continued south. Over P’yongyang it would converge with another train of about equal size that had flown down the western coast. The resulting formation, often containing a hundred or more aircraft, then dropped to an altitude of 15,000 feet to search for fighter-bombers working the railroads. So great was the number of MiGs that the F-86s could no longer effectively screen the F-80s and F-84s. As early as September, MiGs had forced the fighter-bombers to confine their operations to the area south of the Ch’ongch’on River. The MiGs had the initiative by November; they regularly “bounced” the fighter-bombers north of P’yongyang. Losses were few, but the American jets often had to jettison their bombs to escape from their tormentors.
The effect of the MiGs on the operations of Bomber Command was also drastic. The threat that the Soviet-built aircraft posed to the aging medium bombers had been evident since the spring when Bomber Command had been forced to curtail its operations in MiG Alley. The fullness of the danger, however, was not apparent until late October. On October 22, nine B-29s, having just bombed an airfield under construction at Taechon, were jumped by three MiGs after forty others had drawn away twenty-four escorting F-84s. One Superfortress went down. The next day, in a carefully planned interception, fifty MiGs attacked eight B-29s on their way to bomb the airfield at Namsi-dong. Recklessly disregarding fifty-five escorting F-84s, they broke upon the bombers, sending three to earth and seriously damaging the rest. On October 24 eight B-29s, escorted by ten F-84s and sixteen British Meteors, were intercepted by between forty and seventy MiGs. Once again the relatively low-performance escorts could not fend off the attackers, and a Superfortress went down in Wonsan harbor. In Washington a gloomy Vandenberg exclaimed, “Almost overnight, Communist China has become one of the major air powers of the world.” Thereafter the B-29s operated only at night. This conferred, for the time being, immunity from the MiGs, and with the use of a system of radar navigation known as Shoran, the medium bombers were able to attack bridges successfully. But by denying the daytime sky to Bomber Command, its sortie rate was so cut that it could pursue its first priority, the neutralization of the enemy’s advance airfields, only at the expense of the Rail Interdiction Program.
