Japan’s interest in acquiring German uranium


Johann Heinrich Fehler’s U-234.

Japan’s interest in acquiring German uranium was fueled by necessity. Early efforts to locate deposits of uranium within the Greater East Asia Co-prosperity Sphere had revealed only marginal amounts of usable ore; the Japanese army’s procurement director, Gen. Kawashima Toranosuke, recalled that upon witnessing the minuscule amount of uranium produced by the promising Kikune mine in Korea, he “wanted to cry.” Meanwhile, in Europe, Germany had acquired substantial stocks of uranium oxide through the seizure of over 1,000 tons of uranium oxide ore from the Union Minière warehouse in Belgium as well as rich ore deposits in Czechoslovakia. Japan’s wartime industry needed uranium oxide for the extraction of radium, and Japanese physicists also required the ore for experimentation with isotope separation and uranium enrichment. Therefore, on 7 July 1943, Japanese Imperial Army headquarters in Tokyo requested that the Japanese attaché in Berlin, Oshima Hiroshi, approach the Germans concerning “the possibility of exporting to Japan pitchblende (uranium) from the Czechoslovakia region.”

In September, Oshima notified Tokyo that negotiations with the Germans into the matter were progressing, but he needed a statement “showing [uranium’s] importance for purposes of study.” This was an alarming demand; Japanese officials were not used to revealing the exact reasons for their requests. Dr. Nishina Yoshio, Japan’s director of nuclear research, confided to his assistant Kigoshi Kunihiko that he did not wish to disclose his plans for using the uranium to the Germans, who would not stand for Japanese competition in the field of nuclear research. Nishina was investigating isotope separation and uranium enrichment and, if successful, would require substantial amounts of uranium oxide. His need for uranium was critical, and he did not want to jeopardize one of the few sources from which he could obtain the precious ore; any scarcity of uranium would bottleneck his research. Kigoshi suggested that Nishina tell the Germans that the uranium would be used as a catalyst for chemical reactions, thus diverting suspicions that Japanese research rivaled that of Germany. Convinced that the Germans would believe this story, Nishina authorized the formal request and forwarded it to the Japanese War Ministry.

Germany did indeed possess impressive quantities of uranium oxide, and a good deal of the ore was stored at Kiel. German naval munitions experts had discovered that the heavy atomic weight of the substance rendered uranium oxide ideal for the coating of large-caliber naval guns; later in the war the Luftwaffe followed suit and began using the ore in the manufacture of missile warheads. The clamor for uranium oxide for this use was so great that by 1943 the munitions industry’s requests for the ore competed with those of Germany’s atomic researchers in Berlin. Metallic uranium plates, vital for the construction of experimental atomic piles, became a rarity; German uranium suppliers such as Auer and Degussa often explained missed shipments by complaining that the military hoarded most of the readily available stocks of metallic uranium. While it is not difficult to imagine that Germany could have arranged uranium oxide shipments to Japan upon request, it is extremely doubtful that German military and armament officials would have parted with valuable metallic uranium. As a result, most experts agree with Dr. Helmut Rechenberg of the Max Planck Institute for Physics that, given the depleted capacity of German industry to produce metallic uranium during the late war years, it can be assumed “with great certainty that the uranium material [aboard U-234] was not metal but oxide.”

On 15 November, Japan’s Vice Minister of War J. Tory directed Oshima to obtain 100 kilograms (221 pounds) of uranium oxide and forwarded Nishina’s cover story that the ore would be used “as a catalyst in the manufacture of butanol.” Five days later Oshima reported that the Germans possessed substantial quantities from which they would able to supply the requested uranium and “its by-products at present.” However, Oshima was confused as to how much was required; he informed Tokyo that although the latest messages had requested 100 kilograms, “this is an error of one ton compared with the quantity [previously] mentioned. Therefore, please be advised that we will order one ton.”

In Berlin, Oshima forwarded the request to Maj. Kigoshi Yasukazu—who, coincidentally, was the brother of Nishina’s assistant Kigoshi Kunihiko—and directed him to acquire the uranium from the Germans. However, Reich officials viewed the request with suspicion. They did not believe that the Japanese intended to use the uranium solely for chemical experiments or the manufacture of butanol, and therefore refused to ship the ore. This reluctance infuriated General Kawashima, who sent an angry memorandum to German officials revealing that Japan actually desired the uranium for atomic research. In a footnote to his cable Kawashima admonished the Germans for their lack of solidarity and compliance with the Tripartite Alliance, asking, “What is going on here that you don’t want to cooperate?”

Kawashima’s indignation, and Oshima’s considerable diplomatic talents, finally persuaded Berlin to acquiesce. In late 1943 Germany agreed to ship the uranium oxide to Japan via two Japanese submarines. Kigoshi Yasukazu, who coordinated the uranium oxide acquisition, accompanied both consignments to Kiel and supervised the loading of both submarines. The initial shipment, which departed Kiel on 30 March 1944, was lost en route to the Far East when its conveyance submarine, Ro-501, was sunk. However, what happened to the second shipment remains somewhat of a mystery. Kigoshi himself could not verify the fate of the submarine. According to some reports, the boat never left Germany. However, in a May 1945 Associated Press interview, Adm. Jonas Ingram, commander of the U.S. Navy’s Atlantic Fleet, revealed that during the summer of 1944 two Japanese submarines were engaged by American forces off the coast of Iceland. One of these submarines was sunk; the other was only damaged and subsequently escaped. Both submarines had been attempting to access the Atlantic via the Iceland-Faroes passage, the traditional route of U-boats deploying from the North Sea to the Atlantic; it is therefore likely that these two submarines were Ro-501 and her sister boat, both of which had sortied from Kiel. In addition, in a 1953 article in the Japanese journal Dai-horin, Japanese army major Yamamoto Yoichi claimed that in 1944 Japan did receive 500 kilograms (1,100 pounds) of uranium oxide from Germany by submarine. On the basis of this evidence, it appears that the 1943 uranium oxide request was loaded on board Japanese submarines at Kiel, and at least part of the original one ton arrived in Japan in late 1944.

Japan eventually developed reserves of uranium oxide throughout the various territories under its dominion. However, increased requirements from the scientific and military communities soon put a strain on this inventory. In 1944 the Japanese Army Air Technical Department (JAATD) initiated the extraction of 500 kilograms of uranium oxide from the Kikune mine in Korea; however, by the time serial mining began, the JAATD had already requested an additional 500 kilograms. In mid-1944 the Imperial Japanese Navy also asked the Ministry of Munitions for 500 kilograms of uranium oxide. And at the Kyûrikagaku kenkyûjo (Physics and Chemistry Research Institute) in Tokyo, where Dr. Nishina and Kigoshi Kunihiko were attempting to enrich uranium, the dearth of resources had prompted Nishina to request a consignment of uranium as well. Japan’s inventory being of neither the quantity nor the quality to meet these requirements, Germany once again received a request for help from its Axis partner.

In December 1944 Oshima received the request in Berlin and subsequently relayed it to officials of Germany’s overseas-shipping authority, the Marinesonderdienst-Ausland (MSD). MSD officials worked with Kigoshi Yasukazu to coordinate the logistics of gathering the uranium and delivering it to Kiel for loading onto one of three submarines scheduled for departure to Japan in the spring of 1945. In addition, the Marine Sonderstabsweigstellebeinat (Special Naval Home Substation Branch) in Kiel dispatched the MSD’s Commander Becker to various facilities throughout southern Germany to determine “what and how much was to be included in the cargo.” By February 1945 the procurement was complete, and Major Kigoshi met MSD officials in Kiel to organize and oversee the loading of 560 kilograms of uranium oxide onto the next submarine mission to Japan, Johann Heinrich Fehler’s U-234.

The loading of U-234’s uranium oxide is described in Wolfgang Hirschfeld’s memoirs. Hirschfeld stated that each container, “possibly steel and lead, nine inches along on each side and enormously heavy,” was inspected and labeled by the two Japanese passengers, Tomonaga and Shoji. The containers were then delivered to a loading party under the direction of Lt. (jg) Karl Pfaff and lowered into one of the (forward) vertical mine shafts. Hirschfeld also recalled that in addition to Pfaff, Tomonaga, and Shoji, Major Kigoshi was quayside at Kiel, directing the loading of “ten cases of uranium oxide” into the bowels of U-234.

Much of the confusion surrounding U-234’s cargo of uranium oxide arises from conflicting accounts of how the ore was handled once it arrived in America. In Portsmouth most of U-234’s cargo was immediately unloaded, processed, and dispersed to various facilities for testing and evaluation; however, the uranium oxide remained aboard the submarine for a time while American authorities pondered exactly how to dispose of it.

Cdr. Alexander W. Moffat, the surface unit commander of the Eastern Sea Frontier’s Northern Group, was present at U-234’s unloading. In his memoir Moffat stated that the uranium oxide was removed from the submarine the week following her arrival in Portsmouth. He claimed that “the first items to come ashore were the two saddle tanks [which had been] burned free of the deck by welders.” Once the saddle tanks had been secured on the dock, “technicians removed a sample of the contents for laboratory analysis. . . . It seemed to be an odorless granular powder. . . . Word soon spread that the saddle tanks contained uranium.”

The account Hirschfeld gave in his own memoir is vastly different from Moffat’s. Hirschfeld claimed that the uranium was not unloaded until July, when he witnessed six cargo containers lifted from the forward mine shafts and deposited on the dock. Once ashore, the tubes were examined by men “carrying small hand appliances,” which, Hirschfeld was informed, were Geiger counters. Apparently the six containers “were contaminated to such an extent with radiation” that the exact location of the uranium could not be determined. To aid in locating the uranium, Hirschfeld recalled, ONI officials decided to commandeer Karl Pfaff, who had directed U-234’s loading in Kiel.

The disparity between Moffat’s and Hirschfeld’s testimony cannot be easily explained away; in any case, it is certain that Pfaff played an important role in the navy’s disposition of the uranium. Although originally interned in the holding facility at Fort George G. Meade in Maryland, Pfaff had been transferred to the army’s interrogation facility at Fort Hunt in Alexandria, Virginia. On 27 May the Office of the Chief of Naval Operations alerted Portsmouth to information regarding U-234’s cargo that had come to light during Pfaff’s interrogation at Fort Hunt. Pfaff had disclosed that he had been in charge of the cargo in Kiel, both preparing the manifest and personally supervising the loading of all mine tubes. Pfaff had further informed his captors that they should ensure, when unloading the submarine, that the “long containers [were] unpacked in horizontal position and short containers in vertical position,” and he declared himself “available and willing” to aid in the unloading should the ONI desire his help. A return 28 May memorandum from Portsmouth to the CNO reported that the containers had already been unloaded and that Portsmouth was awaiting a CNO directive whether to open the containers there or ship them to Washington for disposition. In reference to Pfaff’s offer of help, the 28 May memorandum also specified that “Pfaff should be available where containers are opened.”

Although Germany and Japan were further advanced in their nuclear programs than first suspected, it is unlikely that the Axis partners had developed a critical-mass reactor or applicable bomb program by the spring of 1945. Stanford University professor Dr. David Holloway points out that in May 1945, when the NKVD’s Gen. Avraamii Zaveniagin’s Soviet scientific mission arrived in Germany to investigate the German atomic program, they found that German scientists “had not separated uranium-235, nor had they built a nuclear pile; nor had they progressed very far in their understanding of how to build an atomic bomb.” The devastation of war at home, the scarcity of essential raw materials, the lack of an extensive government-supported scientific infrastructure, and the absence of a substantial economic and industrial framework all combined to hinder progress. Germany simply could not compete with the United States.

Although the extent of Axis atomic research may not yet be fully understood, U-234’s consignment of uranium oxide was not indicative of any large-scale Axis program, nor did it provide American authorities with any substantial windfall of unique value. Richard Thurston correctly observes that “there is no reason to believe that [U-234’s cargo] contained any elements not readily available to the U.S. and British teams working at Los Alamos and other places.” In all probability, U-234’s cargo was examined, analyzed, and shipped to whichever department needed it; likely destinations might include reactor development, military use, or medical or research purposes. Or maybe, as Thurston offers, tongue in cheek, the cargo is “stored intact in the same cave in Kansas as the Ark of the Covenant.” In any event, U-234’s uranium oxide will continue to mystify and to spark debate. When the big Type XB slipped below the surface of the North Atlantic for the last time in 1947, she left an enduring legacy as one of the continuing controversies of World War II.


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