Special Mission 16: Fat Man and the Atomic Bombing of Nagasaki

Kokura is an industrial city located on the northernmost point of Kyushu Island and ideally situated on the western bend of the Shimonoseki Strait (Shimonoseki Kaikyo in Japanese, also called the Kanmon Strait). During the Pacific Campaign, Kokura was identified as Target Area No. 90.34 by the Allied Joint Target Group. As the shortest route from Korea and the Yellow Sea to the island of Shikoku and the east coast of Honshu, the cities along the Shimonoseki Strait naturally developed as ideal locations for Japanese industry. In the 1930’s and the early years of the Second World War, the area grew to see the heaviest concentration of shipping in the Far East. In addition to Kokura, the cities in this area included Tobata, Wakamatsu, Shimonoseki, Moji, and Yahata (called Yawata by Allied Intelligence, sometimes confused with Yawata City in Kyoto Prefecture).

Kokura’s industrial center was not a large target, estimated to be only 1.5 square miles (3.9 square kilometers) in size by Allied Intelligence. However, inside this small footprint were twelve individually marked targets, foremost among them being the Kokura Arsenal, referred to as Target No. 168, which, in addition to its industrial purpose of manufacturing weapons and equipment vital to Japan’s war effort, also housed a garrison consisting of one Imperial Japanese Army regiment. Allied intelligence reports marked Kokura Arsenal as the largest producer of artillery guns and shells, military vehicles, and small arms ammunition in southern Japan. Particularly concerning for the Allies were unconfirmed reports that peacetime chemical production plants in Kokura were being outfitted with the capability to load poison gas artillery shells and store chlorine, phosgene, and mustard gas.

After the Tokyo Firebombings in early 1945, military materials manufacturing facilities moved from the Tokyo Arsenal down to the Kokura Arsenal. Also in the industrial district were three power plants in Kokura that produced a total of 173,000 kilowatts, of which 90% was used by the surrounding production plants and industries. Additional resources being refined and manufactured in the Shimonoseki Area included pig iron, rolled steel, coke and by-products, aluminum, other non-ferrous metals, coal, and machining equipment.

The Air Objective Folders by Target Area: Japan: Shimonosecki [sic] described the local climate: “Ideal weather for high-level bombing in this area is rare and difficult to forecast without adequate knowledge of existing conditions. Only 36 clear days, on the average, occur during the entire year, but there is an additional unknown number of days with scattered low or middle clouds (sky coverage, 2 to 3 tenths) during which conditions are relatively favorable. Furthermore, when sky coverage consists entirely of high clouds, even though the sky be almost or completely covered, conditions are relatively favorable for high-level bombing.”

Today, Kokura is no longer an independent city. It became two wards, north Kokura and south Kokura, of the conglomerate city of Kitakyushu (literally “North Kyushu” City in Japanese) along with Yahata, Tobata, Moji, and Wakamatsu, which included all of the portions of northern Kyushu along the southern coast of the Shimonoseki Strait.

Nagasaki is a port city on the west side of the island of Kyushu in southern Japan and is the capital city of the prefecture with the same name. Facing the Korean peninsula to the northwest, mainland China to the west, and Taiwan to the southwest, Nagasaki City is in an ideal location for trade, transportation, and industry. Its harbor in Nagasaki Bay is surrounded on all sides by peninsulas and islands that protect ships from the storms and typhoons common in the East China and Philippine Seas.

The city itself is generally divided into two primary river valleys, the Urakami Valley, which contains Nagasaki’s core industries, and the Nakashima Valley, which leads down into the eastern part of the city. Due to the mountainous terrain peaked by Mounts Inasayama, Hokazan, and Konpira, there are many smaller valleys that hug the tributary waterways that eventually empty into the two main rivers or Nagasaki Bay. The mountains and hills surrounding Nagasaki also keep the city’s populace confined to the valleys, leading to many fingers of built up areas that reach up into the forested highlands. In order to make the most use of the limited lowland terrain, the people of Nagasaki created artificial islands and reclaimed land around Nagasaki Bay, altering the waterside areas to build shipyards, wharves, and dry docks to support the ever-busy maritime industry. Even with these extra man-made spaces, the city is densely packed. Prior to World War II, an aerial view of Nagasaki would show irregularly shaped blocks of chōme (city districts) capped with the roofs of wooden or tiled buildings, each at a height different than that of its neighbors.

During the European Age of Discovery, Nagasaki served as one of the very few outlets in Japan where foreign trade was allowed. Dutch, Chinese, and Portuguese traders were able to establish contained districts that facilitated the flow of goods, peoples, and ideas to and from Japan and the wider world. Along with the merchants came Christian missionaries who were allowed to preach and proselytize as permitted by the Japanese officials who controlled the area at the time. However, the times when missionary work was permitted were occasionally punctuated with periods of persecution and expulsion of the European and converted local populations. Despite this, Nagasaki grew to house one of the largest Catholic congregations in Japan. By World War II, Nagasaki’s cityscape of low wooden buildings was dotted with the masonry of churches and cathedrals built in western architectural style.

According to the Army Pathology Institute’s study, “The metropolitan area of Nagasaki is officially reported as approximately 35 square miles [90 square kilometers] in extent, but the built up portion was crowded into an area of about 5.5 square miles [14.2 square kilometers]. Of this, 15% was occupied by industrial installations. In the congested remainder there were no wide streets or pleasant parkways. The houses were built so close together that there was little space for yards or gardens. Here lived a population of about 200,000, so that the general population density in the residential section can be estimated as about 56 per acre.”

The Institute continues:

The Joint Target Group explains the significance of Nagasaki as a Japanese military and industrial target in its Pre-Attack Assessment, dated 5 March 1945:

As Japan began its rapid military modernization program, it required industries and infrastructure to facilitate building, repairing, and supplying the vessels of the Imperial Japanese Navy. By the start of the First Sino-Japanese War (1894-1895), the Mitsubishi Heavy Industries group had established itself as one of the largest military suppliers in Japan. By the start of the Second Sino-Japanese War (1937-1945), Mitsubishi had acres of metalworks, steel mills, lumber yards, dockyards, shipyards, and ordnance facilities in and around Nagasaki. Allied intelligence estimated that the Tategami Shipyard (Target No. 544) alone produced 10-12% of Japan’s naval and merchant marine vessels launched from 1936-1938. The following Japanese warships (with ship class and years active or cancelled) were built by Nagasaki shipyards in the early/mid-20th century and saw action in World War II:

The Nagasaki Shipyards were also tasked to build two auxiliary support ships, 22 escort ships, and 81 motorized torpedo boats between 1941-1944. There were even more vessels built specifically for “special attack forces.” These included six hundred suicide motorboats, one hundred manual torpedoes, dozens of midget submarines, and other hastily constructed vessels, all of which were intended for one-way missions when the Allies began the invasion of Mainland Japan. You can view a more complete list of Japanese shipbuilding plans in the Japanese Naval Shipbuilding Bulletin 142-145, 4 June 1945.

These industries, of which Mitsubishi was only one, became an important part of the Japanese wartime supply effort and were instrumental in building the cargo vessels that would follow in the wake of Japan’s imperial expansion and its establishment of the Greater East Asia Co-Prosperity Sphere. Ships from the Nagasaki dockyards carried men and materiel out to the Japanese colonies scattered across East Asia and the Pacific. Ships returning to mainland Japan carried metal ores, natural rubber, crude oil, and foodstuffs, all of which were domestically scarce resources that Japan needed to import from abroad to fuel its ongoing military conquests, especially after the United States began a series of trade embargoes in 1938.

Japan cited the increasingly harsh American trade restrictions as one of its casus belli when it attacked Pearl Harbor on 7 December 1941. Coincidentally, the Type 91 Mod. 2 shallow-water torpedoes carried by Japanese B5N “Kate” bombers during the attack on Pearl Harbor were manufactured at the Mitsubishi-Urakami Ordnance Works (Target No. 2022) in northern Nagasaki.