UPON U-234’S ARRIVAL in Portsmouth, ONI and navy officials began the arduous task of processing the submarine’s 162-ton cargo. On 21 May, Lt. (jg) John G. Faron, who directed one of the unloading crews, sent Capt. G. R. Phelan a preliminary inventory of U-234’s cargo. In addition to “computers for the ‘Grossbatterie’ system . . . designs for ME 163 . . . igniters for bombs and torpedoes [and] designs and samples of Lorenz 7-H bombsight,” Faron noted “a large quantity of uranium oxide.”1 Two days later U-234’s translated cargo manifest confirmed what would become her legacy: mine-shaft location 38, labeled ST 1270/1–10, contained ten cases, or 560 kilograms (1,235 pounds), of uranium oxide, designated for the Japanese army.2
Since Johann Fehler’s surrender in 1945, U-234’s cargo of uranium oxide has been the subject of debate, prompting much speculation about its presence aboard the submarine as well as the use to which it would have been put had it reached Japan. It is difficult to account for the uranium cargo; many U.S. World War II–era nuclear-related documents remain classified under national security endorsement, and personal accounts often disagree. This examination will consider U-234’s uranium oxide cargo as it is represented in available documentary and primary-source evidence—documents that do not suffer lapses of memory and that reflect the disposition of the precise time at which they were produced.
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.”3 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.”4
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.”5 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.6
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.”7
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.”8 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.”9
In Berlin, Oshima forwarded the request to Maj. Kigoshi Yasukazu—who, coincidentally, was the brother of Nishina’s assistant Kigoshi Kunihiko10—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?”11
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.12 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.13 However, what happened to the second shipment remains somewhat of a mystery. Kigoshi himself could not verify the fate of the submarine.14 According to some reports, the boat never left Germany.15 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.16 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.17 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 1944.18
Japan eventually developed reserves of uranium oxide throughout the various territories under its dominion.19 However, increased requirements from the scientific and military communities soon put a strain on this inventory.20 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.21 And at the Kyûrikagaku kenkyûjo (Physics and Chemistry Research Institute) in Tokyo, where Dr. Nishina and Kigoshi Kunihiko were attempting to enrich uranium,22 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.23
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.”24 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-234.25
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-234.26
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.”27
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.28 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.29 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.”30
Pfaff had revealed that the uranium oxide was packed in “gold-lined cylinders [and] as long as cylinders not opened can be handled like crude TNT. . . . The containers should not be opened as substance will become sensitive and dangerous.”31 This assessment presented the navy with two problems. First, it raised the possibility that the containers had been wired with explosives to prevent the rare ore from falling into enemy hands. And even if the containers were not booby-trapped, navy officials still had little information about the safety issues involved in handling uranium oxide; in 1945 the handling of radioactive materials was not something with which most naval personnel were familiar. For this reason American intelligence officers approached Pfaff during his interrogation at Fort Hunt and asked the young German to accompany them and supervise the opening of the uranium containers.
In a 1995 interview, Pfaff recalled that he was escorted to “a large arena in Indian Head, a naval station on the Potomac River, where all the cargo was spread out.” He concluded that this place was a depository for “a lot of secret stuff”; he did not realize at the time that Indian Head, Maryland, was home to the U.S. Navy’s Ordnance Investigation Laboratory and the Naval Powder Factory, a logical venue for analysis of the uranium oxide.32
Prior to Pfaff’s arrival, naval investigators had X-rayed the containers and had mistaken the internal handling devices, which were actually wooden poles, for booby traps.33 As a result, when Pfaff arrived he encountered a rather nervous enlisted man who had been assigned to cut the containers open with an acetylene torch. Before cutting into the cylinder, the rating turned to Pfaff and lamented that he had a wife and kids; he didn’t want to die. Pfaff reminded the man that if the cylinder was booby-trapped, he (Pfaff) would be blown to bits too. Besides, the cargo was intended for the Japanese; why would Germany seek to “blow them up”? His fears abated, the sailor proceeded to cut the containers open.34 Other than a small fire caused by the torch igniting rags that had been used to pack the items inside the cylinders, the opening of the cargo containers proceeded without incident.35
Pfaff’s chronology of his stay at Indian Head is supported by a 23 June 1945 memorandum from T. F. Darrah, commanding officer of the Indian Head facility, to the chief of the navy’s Bureau of Ordnance (BuOrd) and a Lieutenant McQuade of the ONI. Darrah reported that on 23 June his activity shipped eleven items, which he identified as cargo containers from U-234, although he did not designate their destination.36 However, the 2 July 1945 agenda for a meeting of a “Washington Group Trust” described item number 2 as “a report on captured material from German U-boat U-234” and identified the location of the material as a warehouse in Brooklyn, New York.37 Whether this material was U-234’s uranium oxide is not clear; however, other items on the agenda were related to uranium matters, and given the alternative repositories for the ore, it is likely that the uranium oxide was shipped to the Brooklyn location pending further disposition.38
The destination of U-234’s uranium has also been the subject of conflicting accounts. In a 1995 interview Maj. John Lansdale, former head of security for the Manhattan Project, stated that U-234’s uranium went directly to the Manhattan District’s processing facility at Oak Ridge, Tennessee. Proponents of this account postulate that once at Oak Ridge, the uranium was processed and used in one of the atomic bombs dropped on Hiroshima and Nagasaki. The notion that uranium originally intended for Japan eventually reached its destination, albeit not in the desired form, is attractively ironic; however, this scenario is unlikely. Lansdale admitted that he recalled no details as to what happened to the uranium after it was sent to Oak Ridge and therefore could offer no opinion as to whether it was used in either the Hiroshima or the Nagasaki bomb.39 As Dr. Philip Morrison, a professor of physics at the Massachusetts Institute of Technology and a former Manhattan Project official, points out, “It is highly unlikely time would have allowed the uranium to make it into the Manhattan Project bombs.”40
The accounts of Lansdale, Moffat, and Hirschfeld are sufficiently diverse to arouse curiosity; of such multiplicity are legends born. How do we separate legend from fact?
Given the ominous nature of the uranium oxide, it is unlikely that American intelligence personnel would have left the cargo aboard U-234 from mid-May until July, as Hirschfeld recalled. The expediency shown by Portsmouth, the ONI, and the CNO’s office in unloading the containers and enlisting the aid of Karl Pfaff to open them supports this assumption. Commander Moffat’s and Major Lansdale’s accounts are similar to one another. Lansdale relegates the uranium oxide to Oak Ridge and so provides a convenient destination. Moffat’s assertion that the saddle tanks, containing the uranium in powder form, were opened on the dock is inconsistent with all other accounts of the physical appearance and location of the uranium, and it could be regarded as an “official explanation.” It must be remembered that both Moffat and Lansdale were dedicated career military officers operating in the sensitive operational environment of 1945. Their judgment concerning national security interests no doubt shaped their accounts.
Whatever the discrepancies between the accounts of the various individuals involved, the basic facts and sequence of events can be pieced together from the official documentation as follows. The 27 May memorandum from the CNO to Portsmouth reported Pfaff’s ominous description of the cargo (“loaded in gold-lined cylinders . . . sensitive and dangerous”) and his offer to help unload the ore. The 28 May memorandum from Portsmouth to the CNO stated that the containers in question were “off ship and ready for shipping. . . . Request decision whether cargo containers opened here or shipped to Washington. . . . Pfaff should be available where containers are opened.” (Interestingly, both memoranda included the chief of the Bureau of Ordnance on their restricted distribution lists.) In a 1995 interview Pfaff stated that he was at some point taken from Fort Hunt to Indian Head; he did not recall the exact date, but from the 27 and 28 May CNO memoranda we can deduce that it must have been in early June 1945. Subsequently, in a 23 June memorandum the commanding officer at the Indian Head Ordnance Investigation Laboratory, T. F. Darrah, notified the chief of the Bureau of Ordnance that he was releasing eleven items from U-234, all of which bore identifying numeration consistent with that of other cargo containers unloaded from U-234. Finally, the 2 July 1945 agenda of the Washington Trust Group, which, according to other items on its agenda, was primarily concerned with matters relating to uranium, disclosed that the group was going to discuss “material from U-234,” stored in a warehouse in Brooklyn. This is the most logical account of the handling of U-234’s uranium cargo, and the one most likely to be true. The trail of U-234’s uranium oxide ends in Brooklyn; no other official documentation or compelling personal testimony has yet revealed the ultimate destination of U-234’s cargo.
A farther-ranging controversy involves the physical nature of U-234’s uranium. Uranium oxide is a compound of low radioactivity and emits no harmful gamma radiation. The fissionable isotope uranium 235 must be removed from uranium oxide through the process of isotope separation; to achieve high levels of radiation, it must be processed in a reactor. During World War II the United States possessed the world’s only known functional reactor, although Germany and Japan were working to develop their own. However, Hirschfeld said that in his opinion the uranium oxide loaded aboard U-234 was “highly radioactive.” In addition, he claimed that prior to loading, U-234’s Japanese passengers Shoji and Tomonaga wrote “U235” in black characters on the “brown paper wrapping [that was] gummed around each of a number of containers of uniform size,” implying that the boxes contained radioactive uranium in metallic form.41 Once at Portsmouth, Hirschfeld recalled American officials arriving with Geiger counters, which allegedly verified that the cargo was sufficiently radioactive to have contaminated the entire forward area of the submarine. Pfaff, meanwhile, had revealed that the cargo containers were lined with gold, an effective shield against radioactivity. Do these assertions indicate that U-234 was carrying fissile material to Japan, which by proxy would prove the existence of a functional German nuclear reactor during the war years?
Once again, inconsistencies in personal testimony add to the confusion. Whereas Hirschfeld described Tomonaga and Shoji as actively participating in the loading of the ore, inspecting and labeling it, Pfaff claimed that “the Japanese passengers on board were not concerned with the uranium. . . . They were just passengers trying to get home to Tokyo.”42 Moreover, according to British author Geoffrey Brooks, who translated Hirschfeld’s memoirs and has interviewed him extensively, Hirschfeld “was not close to the loading operation” in Kiel and prior to 1992 did not know how many cases were involved in packaging the uranium. During the loading, Hirschfeld was on U-234’s conning tower; his closest proximity to the loading operation would have been about 70 feet. At that distance it would have been difficult to tell whether the containers were cylindrical or cubical, and to see exactly what the Japanese were writing on the packages.43
Furthermore, author Richard Rhodes points out that the label “U235” “can’t possibly mean [that] the boxes contained U235. . . . [The United States] labored mightily in vast separation plants to accumulate the sixty kilograms we used in Little Boy.”44 The presence of 560 kilograms of radioactive uranium 235 would indicate German uranium separation on such a massive scale that the whole world would have known of it. Rhodes concludes that “the likeliest content of [U-234’s] containers was refined ore for reactor development.”45 Dr. Michael Thorwart at the University of Augsburg’s Institut für Physik confirms that Germany never possessed a critical reactor; while Werner Heisenberg’s group had succeeded in improving neutron production in Haigerloch, substantial gains were not realized until April 1945. There is no conclusive evidence that Germany had developed an operational reactor by the end of the war, much less one that could operate on a scale sufficient to produce the amount of material aboard U-234. In Tailfingen Dr. E. Bagge developed a working isotope separation device; however, it also became operational too late to aid the German war effort, first achieving separation only on 24 April 1945.46
As for Pfaff’s contention that the contents of the cylinders would become sensitive and dangerous upon opening, Rhodes explains that powdered uranium oxide is pyrophoric and ignites when exposed to air, a problem that American physicists faced during the early days of American reactor development. In addition, highly irradiated material is “physically extremely hot and radioactively highly penetrating. . . . I doubt if the gold lining [of the cylinders] would have been sufficient to contain [the radiation] had it been highly irradiated.”47
Lt. Col. Richard Thurston, a former U.S. Army biologist and radiological warfare expert, proposes another explanation for U-234’s radioactivity. Thurston points out that the contents of the containers might have been radium or a radium compound, which would explain both the radioactivity of the cargo and the need for gold shielding. In addition, radon gas escaping from the radium could have permeated the submarine’s cargo area, rendering it difficult to determine which mine shafts held the radioactive cargo.48 In any event, according to Dr. Kigoshi Kunihiko, the wartime assistant to Japan’s director of nuclear research, the entire episode is irrelevant: “If the uranium loaded on U-234 was neutron irradiated, it seems very hard to suppose that Japanese scientists at that time [could] evaluate and . . . treat properly such processed uranium.”49
The U.S. Army’s Alsos mission also raised questions about the true nature of U-234’s ore. An 18 July 1945 Alsos intelligence report revealed the discovery of substantial quantities of various alloys in Germany. In this report H. S. Van Klooster, an Alsos expert consultant, described a 1943 German secret investigation into the characteristics of pyrophoric thorium and cadmium alloys with “copper, silver, and gold up to fifty per cent atomic weight.” Van Klooster also observed that German metallurgists had experimented with powdered alloys that “caught fire spontaneously when kept in air. . . . The spontaneous combustion is most pronounced in the case of silver-thorium or gold-thorium alloys.”50 The volatility that Pfaff attributed to the contents of the containers—he contended that the material would become unstable when opened—would be consistent with one of these pyrophoric alloys. In addition, in a 1984 letter U-234 passenger Kay Nieschling wrote that the cargo “concerned a cadmium alloy that [the Americans] were not yet familiar with over there.”51
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.”52 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.”53 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.”54 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.