The Japanese ambassador to Berlin who involuntarily made Normandy landings easier to the Allies

Image: The Emperor’s Codes

Although intelligence services were consecrated above all in the Cold War, they had already had more or less important roles throughout History. In that sense, it is possible to consider among the best agents that have ever existed, one that operated during the Second World War, providing a thousand and a half reports to the Allies, to the point of being described by General Marshall as “our main source of information regarding Hitler’s intentions in Europe”. The irony is that this spy was not such; it was Baron Hiroshi Ōshima, the Japanese ambassador to Berlin, whose dispatches to his government were intercepted and deciphered without his knowledge.

Ōshima, born in the prefecture of Gifu in 1886, was of noble family and already carried in his blood the public service because his father had been Minister of War from 1916 to 1918. He entered the Rikugun Shikan Gakkōla (Academy of the Japanese Imperial Army), obtaining the office of lieutenant in 1908. He then attended the Rikugun Daigakkō (Army War School) and was promoted to captain in 1915. His first destination was Siberia, in the intervention that the Japanese executive carried out between 1918 and 1922 to stop the Bolshevik Revolution’s eastward expansion and to seize the port of Vladivostok first than the British.

Japanese postcard showing their troops occupying Blagovéshchensk/Image: public Domain on Wikimedia Commons

In that context, Japan had moved away from its allies in the First World War (France, Great Britain, USA) to approach Germany gradually, although without supporting it warily. When the war ended and the Weimar Republic was proclaimed in that country, Ōshima was sent to the embassy in Berlin as deputy military attaché, a post he later held in other legations such as Budapest (1923) and Vienna (1924). In the meantime he ascended the ranks and in 1930, five years after returning to his country, he reached the rank of colonel, receiving command of an artillery regiment.

But it was felt that his services would be more useful in diplomacy and, specifically, at Berlin, since he had learned to speak German. So in 1934, with the Nazi regime fully in power, he returned to the embassy as a military attaché. Ōshima sympathized with Nazism and befriended the German foreign minister, Joachim von Ribbentrop, and actively collaborated with him in the drafting of the Anti-Komintern Pact, signed in 1936 by Adolf Hitler and Ambassador Kintomo Mushakoji (on behalf of the prime minister Kōki Hirota) to contain communism and create Manchukuo (a puppet state in Manchuria), later joined by Italy, Spain, Hungary and others.

Hiroshi Ōshima in Lieutenant General uniform/Image: public Domain on Wikimedia Commons

In fact, it was said that this treaty was promoted by Ōshima without the Japanese Ministry of Foreign Affairs, and this was stated by Joseph Grew, U.S. ambassador in the German capital, which is significant in two ways: on one side, it demonstrates the ideological affinity of the military attaché towards the Hitler regime (“he was more Nazi than the Nazis” was said of him); on the other side, it reveals the level of knowledge that the U.S. embassy had about the activities of the Japanese, who two years later was not only promoted to lieutenant general but became ambassador.

In this new post, he further strengthened his relationship with Ribbentrop and acquired greater capacity to act as a visceral anti-communist, organising an operation to kill Stalin in conjunction with Russian agents – which evidently did not materialise – as well as expressing to the Teutons his desire to agree on collaboration aimed at putting an end to the Soviet Union, which Japan still saw as a danger very close to its borders. Ōshima’s devotion to Nazism was such that the government, which had ordered him to return to Japan in 1939, annoyed by the signing of the Ribbentrop-Molotov Pact, reinstated him in office again in 1941 at Berlin’s request.

One of Hiroshi’s frequent encounters with Hitler /Image: public Domain on Wikimedia Commons

He would no longer move from the German capital until the end of the Second World War, a conflict in which his country would enter that same year making effective from 1940 to be part of the Tripartite Pact or Axis Pact along with Germany and Italy. Ōshima offered total cooperation in war and that had an obvious field of operations: the Pacific. In exchange for attacking the colonial possessions of the British Empire, Ribbentrop promised help if Washington interfered. In the end, Japan opted to hit Pearl Harbor first (December 7, 1941) and Hitler not only applauded the operation but honored Ōshima with the gold cross of the Verdienstorden vom Deutschen Adler (Order of the German Eagle).

But that collaboration went beyond that. On January 3, 1942, the Japanese ambassador agreed with Germany to sink the lifeboats of torpedoed enemy ships in order to trouble the Allies in the availability of troops, in case they could not be taken prisoners, a frequent occurrence in the ocean. “We are fighting for our existence and our attitude cannot be governed by any human feeling” was Hitler’s explanation, approved by Ōshima. In 1944 that way of acting was aggravated with the execution of the downed pilots.

The Japanese embassy at Berlin, decorated for the signing of the Tripartite Pact/Image: Bundesarchiv, Bild, on Wikimedia Commons

There was only one thing that the ambassador could not achieve: that Japan declared war on the Soviet Union when the Germans began the invasion of that country in June 1941, given that two months earlier Tokyo and Moscow signed a non-aggression pact. In fact, Ōshima was not even informed until Operation Barbarossa began; the Japanese were then invited to unite to remove the Russian threat in Asia once and for all. However, Japan declined the offer because it was unable to deal with so many fronts at once.

As can be seen, Ōshima maintained close contact with Ribbentrop and the Führer, which gave him access to substantial military information, both in terms of strategy and technical data. Much of this was written in reports that he then radioed to his government in encrypted code, using a Japanese version of the famous ENIGMA machine. What the Japanese did not know was that the American intelligence services, which named the device PURPLE, discovered its coding system back in 1940.

Joachim von Ribbentrop and Hiroshi Ōshima in 1939

Therefore, everything that was transmitted between Germany and Japan by that means also reached US experts, sometimes even in less time. Worse still, not only the Americans but also the Soviets benefited, since because of the distances many communications were made through the Japanese embassy in Moscow and the NKVD (Naródny Komissariat Vnútrennij or People’s Commissariat for Internal Affairs; the state security services) had the codes. They had been obtained by Walter Krivitsky, one of his agents infiltrated in Berlin, in 1936, on the occasion of the German-Nippon negotiations of the Antkomintern Pact.

It is estimated that virtually all communications from Ōshima to Tokyo were intercepted and decrypted: around a thousand and a half in just over four years, despite the fact that the Germans warned him how unreliable their ciphers seemed to them. That huge security failure cost them serious adversities, some of them well known, such as the death of Admiral Yamamoto when his plane’s schedule and course were discovered; others not so much like the case of the diversion of the North American tankers, which stopped supplying themselves in Spain in 1944 when they learned that there operated a Japanese espionage network called TO informing of their departures.

Part of a PURPLE Type 97 machine found at the Japanese embassy in Berlin/Imagen: public Domain on Wikimedia Commons

Ōshima was a goldmine in providing information not only to combatants but also to later historians: for example, by describing in his messages what the effects of the bombings on cities were, outlining the number of casualties, the damage caused, etc. It was very valuable because it was an objective, descriptive testimony, formally distanced from more personal ones such as the one he made in 1941, without too much discretion, predicting that Great Britain would end up surrendering at the end of the year.

Now, probably the biggest mistake of Ōshima in that sense was the one he committed in 1943. In November of that year he toured Atlantikwall (Atlantic Wall, the chain of defenses – bunkers, trenches, batteries … – built on the shores of that ocean in the so-called Operation Todt with the aim of stopping the invasion that was known to be imminent) and wrote a detailed report of twenty pages that, of course, ended in enemy hands. This greatly facilitated the design of the plans for Operation Overlord (the famous Normandy landings) to the point that the Allies knew that the bulk of the troops would not be in Normandy but in Calais, as well as taking note of the type of obstacles and resistance they would encounter.

Hiroshi Ōshima, together with Japanese and German officers, visiting the Atlantic Wall in 1943./Image: Bundesarchiv, Bild, on Wikimedia Commons

Although the balance of war was increasingly tilted towards the adversary, the Japanese ambassador remained convinced of Hitler’s final victory, refusing to leave Berlin with the other diplomats when the front reached the outskirts of the city and expressing his desire to remain with his friends in the Third Reich until the end. However, the order to leave the capital was categorical and along with the rest of his legation he left for Austria, where his wife awaited him, on April 14, 1945.

A few weeks later Germany capitulated and the Japanese diplomats surrendered to American forces, being sent to the United States. They remained there for four months, after which they were able to move to Japan. But it was an ephemeral freedom. In December of the same year, Baron Hiroshi Ōshima was arrested again, accused of being a war criminal.

A session of the Japanese war criminals trial/Image: public Domain on Wikimedia commons

He was tried by IMTFE (International Military Tribunal for the Far East), popularly known as Tokyo War Crimes Tribunal, which found him guilty and sentenced him to life imprisonment in 1948. However, times had changed to the point that Foreign Minister Mamoru Shigemitsu (who had the lightest sentence, seven years) not only got parole in 1950 but won the elections four years later, so all other convicted ones were pardoned in 1955, Ōshima included. He died in 1975.


Sources: Historical Dictionary of German Intelligence (Jefferson Adams)/Japan, Italy and the Road to the Tripartite Alliance (Ken Ishida)/Marching Orders: The Untold Story of World War II (Bruce Lee)/Hitler’s Japanese Confidant: General Ōshima Hiroshi and MAGIC Intelligence, 1941-1945 (Carl Boyd)/Historical Dictionary of Japan to 1945 (Kenneth Henshall)/A Century of Spies: Intelligence in the Twentieth Century (Jeffery T. Richelson)/Battle of Wits: The complete story of Codebreaking in World War II (Stephen Budiansky)/Intelligence and the War Against Japan: Britain, America and the Politics of Secret Service (Richard J. Aldrich)/The Emperor’s Codes: Bletchley Park and the breaking of Japan’s secret ciphers (Michael Smith)/Wikipedia