The XI Corps gradually overcame the Shimbu force's southern pocket. By early May it had surrounded 4700 combat troops at the juncture of the Ipo and Angat rivers. Another force of about 2700 men was cornered in the vicinity of Santa Maria-Bosoboso, and 6200 more were holding the Mt. Oro-Mt. Pamitinan-Mt. Purro area. The corps expected desperate opposition. Late in April General MacArthur had called attention to the inadequate water supply reaching Manila and directed that the Ipo Dam be captured as a priority objective. It was seen that if this reservoir continued in enemy hands or was destroyed Manila faced an epidemic of enteric diseases. New and speedier tactics of attack were in order.

The V Fighter Command accordingly prepared for the largest mass employment of napalm in the Pacific war. On 3–5 May 1945 a total of 238 fighters saturated the outlying defenses of the Ipo area with napalm and demolition bombs. These attacks proved very destructive and extremely demoralizing to the enemy, driving them into the open where they were easy targets for other forms of attack. The V Fighter Command repeated the same general pattern of attack on 16–18 May. Operations officers divided the five-square-mile area held by the Japanese into sectors and then sent 673 Lightnings, Thunderbolts, and Mustangs to turn it into a sea of flames. Napalm-laden P-38's and P-47's, flying at 50 to 100 feet, attacked first, followed by P-51's which strafed and bombed the terrified Japanese. On the second day A-20's with frag bombs aided the Mustangs. As our 43d Division moved ahead against negligible resistance, it estimated conservatively that 650 Japanese had been killed by air action alone. Approximately 1500 other fatalities among the enemy in this action were attributed to machine-gun and mortar fire by ground forces.

The Ipo Dam, although prepared for demolition by the enemy, was captured without damage.

The employment of napalm in the liberation of this objective drew comment in the United States Strategic Bombing Survey:

Napalm became a primary weapon in close support in the SWPA as soon as it became available in quantity late in the war. In the Ipo Dam area west of Manila, the Japanese were holed up in five strongholds embracing almost a square mile. Five fighter groups delivered a total of 646 sorties, dropping 200,000 gallons of napalm to enable our ground troops to walk, standing up, into the enemy strong points where weeks of probing prior to the fire bomb attacks had failed to show a soft spot.

Korean War situations

Destruction of Sinuiju. In the air battle for the Yalu during the early stages of the Korean campaign, the mission of the Far East Air Forces was to effect a complete interdiction of North Korean lines of communication and the destruction of North Korean supply centers and transport facilities, North Korean ground forces, and other military targets bearing immediately upon the current tactical situation. In a USAF historical study on Air Force operations during that campaign the fulfillment of the mission is recorded:

In recognition of the massive destruction capabilities of the B-29 medium bombers, much of this effort was delegated to the FEAF Bomber Command. Fifth Air Force would provide fighter escort and combat air patrols so as to maintain air superiority, would under

take such destruction of hostile supply centers and interdiction targets as was practicable with its fighter bombers and light bombers, and would maintain reconnaissance over enemy lines.

Because of the urgency of the task and the reduction of medium bomber strength to three groups, FFAF secured a relaxation of the policy preventing use of incendiaries against Korean targets, directing FEAF Bomber Command (P) "to employ any type of ordnance which will best accomplish its object." Lt Gen Earle E. Partridge was similarly authorized to "utilize any ordnance available." [Not to include nuclear weapons.-Ed.] High-explosive general-purpose bombs were recommended for attacking the approaches to the main bridges across the Yalu and the marshalling yard at Sinuiju.

FEAF target planners had given careful attention to the North Korean city of Sinuiju on the south bank of the Yalu directly across from the Manchuria city of Antung. A bombing attack would provide an additional restriction to the movement of military supplies from Manchuria into Korea and would destroy warehousing and accumulated stacks of military goods. In October, FEAF had directed Bomber Command to conduct on 7 November 1950, a maximum effort B-29 strike designed to destroy the key enemy communications and supply center at Sinuiju. The Fifth Air Force would provide fighter escort and combat air patrol for the bomber force.

As a warm-up on 5 November, Bomber Command sent 22 B-29's to drop incendiaries on barracks and warehouses at Kanggye, a north central Korean town at the apex of transportation routes leading southward to Sinanju and Hamhung; the attack destroyed more than 65 percent of Kanggve's built-up area.

On 8 November, 79 B-29's dropped on Sinuiju 584.5 tons of 500-lb incendiary clusters and 1,000-lb bombs, the latter being aimed at approaches to the international bridges. Comparison of pre-strike and post-strike photographs showed that over sixty percent of the 20,000,000 sq ft built-up area of the city was destroyed. Fifth Air Force provided a fighter escort, and a preliminary fighter bomber strike against flak installations which considerably reduced the volume of enemy ground fire. Other enemy guns on the Manchurian shore threw up a heavy volume of fire, but the bombers came over Sinuiju at 18,000 to 21,000 feet and escaped damage.

This Bomber Command strike against Sinuiju virtually eliminated the first of ten priority communications and supply centers designated by General Stratemeyer.

A consideration of the type of ammunition employed, the quantity in tons expended, and the area covered in these actions prompts the observation that, had atomic bombs of infinitely smaller weight but almost incalculably higher yield been dropped upon these targets, greater destruction would have been achieved and the neutralization of enemy potential would have been more lasting. A further advantage would have been gained in that the drops could have been made from altitudes beyond the range of enemy antiaircraft.

The bombed areas were suitable as atomic targets, since they were clearly defined in intelligence dossiers and well depicted in reconnaissance photography.

Battle for the Yalu bridges. The United Nations air interdiction effort ordered the destruction of the first span out from the Korean bank of the Yalu River bridges and marked for destruction every major bridge structure between the Yalu and the battle line. Concurrently the Fifth Air Force was laying an all-out armed reconnaissance, by night and day, against everything moving on North Korean road and rail routes.

In all, there were 12 international bridge crossings of the Yalu. The most important of them to the tactical situation were those in northwestern Korea: the combination rail and highway bridge and the double-track railway bridge at Sinuiju, the highway bridge at Chongsongjin, the railway bridge at Namsanni, the highway bridge and railway bridge at Manpojin. Across the Sinuiju, Chongsongjin, and Namsan-ni bridges the Communists could run forces to oppose the Eighth Army. The Manpojin bridges would permit the Chinese to march down the center of North Korea and split the Eighth Army from X

Corps. Other bridges of lesser importance to the tactical situation were the highway structures at Ongdmdong, Linchiang, the two at Hyesanjin (this town was occupied by U.N. forces on 20 November), at Samanko, and near Hoeryong.

In deference to the fact that these bridges were major steel structures, built by the Japanese to withstand great natural adversities, the Yalu bridges were assigned as FEAF Bomber Command targets. Effective 8 November Bomber Command was directed to destroy the bridges at Sinuiju, Namsan-ni, Chongsongjin, Manpojin, and Hyesanjin, and by 17 November the entire list of bridges had been authorized for attack. On 12 November, noting that much of its B-29 effort had to be committed to the destruction of enemy communications and supply centers, FEAF requested that Navy-based air assist in the destruction of the international bridges. FEAF medium bombers had developed a high degree of proficiency during the bridge-interdiction campaigns in South Korea, bombing from an altitude of 10,000 feet with little or no opposition. But even under these favorable circumstances the 19th Bombardment Group had been hard put to destroy the steel cantilever west railway bridge at Seoul, an effort which ultimately consumed 86 sorties and 643 tons of heavy demolition bombs.

Bombers of the 19th Group began attacking the Yalu River bridges on 8 November under cover of the massive attack against the Sinuiju bridges. Following this attack, medium bombers did not again return to the Sinuju bridges until 13 November, when nine 98th Group B-29's walked their bombs across the bridge approaches and covered both bridges well out to midstream. With three flights in close trail, the 98th Group passed over the target within ten seconds, thus minimizing the time of exposure to antiaircraft fire. On the following day Bomber Command sent a normal three-group effort against the Sinuiju and Manpojin bridges. Twenty-one B-29's of the 19th and 307th Groups fought off Mig and Yak attacks to drop 111 tons of 1000- and 2000pound general-purpose bombs in good pattern on the Sinuiju bridges. But the damage was slight, probably because of the flak and fighters, which badly damaged two 307th Group B-29's, and because of the drift caused by a 95-mph crosswind.

On 24 November weather improved, and all three medium bomber groups went out on interdiction missions, ranging from the Yalu to the bomb line. The 98th Group, with eight B-29's, laid down its 1000-pound bombs at the Manpojin railway bridge. While most of its bombs were accurately aimed, flak-evasion maneuvers and 17° drift caused some eight bombs to fall in the mud flats on the Manchurian side of the river. Seven 19th Group planes dropped 2000-pound bombs on the international highway bridge at Chongsongjin. Next day four 19th Group B-29's had disappointing results at Chongsongjin, but eight other planes of the group reported destruction of at least one span of the Manpojin railway bridge. Enemy antiaircraft fire at Manpojin (a great proportion of it coming across the Yalu) was now so severe that Bomber Command was authorized to suspend attacks on the bridges and instead effect multiple cuts on the railways and highways south of that city. On 26 Novem

ber eight 307th Group B-29's reported two spans of the Chongsongjin highway bridge in the water, but the status of this bridge remained in doubt. The 307th Group sent eight more B-29's there on 29 November to score hits on two spans. The 19th Group repeated the raid on 30 November with eight B-29's, which reported destruction of one span of the bridge. Because of a rack malfunction the 19th Group let one 4000-pound general-purpose bomb slip across the border to the Manchurian shore.

Meanwhile the planes of the aircraft carriers Leyte, Valley Forge, and Philippine Sea had gone into action against the international bridges on 12 November. The Sinuiju railway bridge proved as invulnerable to the Navy dive bombers as to the B-29's. “Knocking down that Sinuiju railroad bridge,” commented the Leyte's air group commander, "was like tackling San Francisco's Golden Gate." The Sinuiju cantilever-span highway bridge was more vulnerable: a three-day attack dropped its Korean approaches. Navy strikes also damaged the Manpojin railway bridge and cut single spans out of the two bridges at Hyesanjin. Navy pilots reported severe antiaircraft and enemy fighter opposition; they too were forced to attack targets from inopportune bomb-run angles lest they violate Manchurian territory.

By the end of November the U.N. air effort had succeeded in cutting at least four of the international bridges and had damaged most of the other bridges, but it was becoming increasingly evident that the returns were not commensurate with the effort expended.

Here again, the superiority of atomic ordnance over the types of weapons considered conventional at the time of the Korean campaign suggests itself. Precisely what expenditure of nuclear bombs would have equaled the destructive effect of the high explosives (HE) dropped upon the Yalu River bridges could be readily computed, given the exact tonnage and type of HE used. But it becomes apparent without such computations that with nuclear weapons the total effort required to launch the Yalu sorties could have been very greatly reduced and the CEP'S (circular probable errors) more accurately controlled to conform to the restrictive limitations imposed by high authority.

Action in the Pusan perimeter. On 5 July 1950, less than two weeks after hostilities had begun in Korea, the Commander in Chief, Far East (CINCFE), ordered the establishment of a joint operations center (JOC) at the 24th Division headquarters in Taejon as well as a tactical control center (TACC) near that city. Within two days of the setting up of these facilities enemy troops and armor had advanced into this general area and were building strength along a line between Pyongtaek and Wonju. Faced with this situation, CINCFE directed that medium-bomber missions originally planned against Wonsan, Seoul, and Pyongyang be devoted to attacks on bridges in the battle area in an attempt to reduce the flow of troops and supplies to the front.

Soon afterward the enemy launched drives against Taegu, where the Joc and TACC had been compelled to locate by the suddenly deteriorating situation, and immediately initiated a pincer movement on Taejon, forcing U.S. units to set up defensive positions facing the enemy attack. On 19 July the enemy opened the assault on Taejon with artillery and mortar fire, forcing U.N. troop withdrawal three days later to positions along the east bank of the

Naktong River. On 7 August the enemy crossed the Naktong at several points, suffering heavy casualties as U.S. forces resisted. Nevertheless within three days enemy bridgeheads east of the Naktong were reinforced with additional troops and supplies. For the rest of August enemy patrol action along the river was extensive. On 1 September the enemy launched a general offensive, making his deepest penetration north of the junction of the Naktong and Nam rivers. It was not until mid-September that U.S. units reduced the threat of his offensive in that sector. The turn in the tide was largely attributable to "carpet bombing" tactics of the B-29's of FEAF'S Bomber Command in troop assembly

areas.

The troop concentrations in the Naktong valley during the Communist thrust of July and August 1950 would have afforded profitable targets for atomic attack had the weapons been available in their present assortment and had other conditions been permissive. Circumstances prohibiting nuclear warfare during the Korean campaign are still recent enough at this writing to recall that considerations against its practice were more political than military and that the political implications were international, since the United States, the possessor of the atom bomb, was allied with several other of the United Nations in the Korean expedition.

Atomic weapons in the Korean War. During December 1950 there was some thought as to the practicability of using atomic weapons in Korea. The Eighth Army staff was reported to be in favor of their employment, and the Fifth Air Force saw no reason why it could not mark targets for an atomic strike, provided that proper targets could be located.

A theoretical study undertaken by an Army research organization later claimed that lack of ground and air intelligence at that time regarding Communist troop movements and concentrations would have limited the destructivity of atomic weapons had they been tactically employed against hostile personnel targets. Had intelligence been better, atomic weapons might have taken a terrible toll of hostile troops.

The study estimated that, if one 40-kiloton airburst weapon had been exploded over the dense enemy concentration in the Taechon area on the night of 24-25 November 1950, 15,000 of a total enemy force of about 22,000 troops would have been destroyed. It was estimated that casualties from six 40-kiloton airburst bombs over the fairly extensive enemy assembly in the Pyonggang-Chorwon-Kumhwa triangle on 27-29 December 1950 would have amounted to some 30,000 to 45,000 of a total enemy force of about 65,000 to 95,000, had intelligence regarding enemy numbers been exact and timely. Had six 40-kiloton bursts been laid along the enemy lines north of the Imjin River on the night of 31 December-1 January 1950–51, an estimated 28,000 to 40,000 of a total enemy force of 70,000 to 100,000 in the area preparing for a jump-off assault against the Eighth Army would probably have been destroyed.

Logistics

In the preceding discussion the figures given for various battles and campaigns indicate even to the uninitiated the tremendous logistic effort required