In November 1943, an intercept operator named Leonard Mudloff sat down at a receiver in a converted barn at Vint Hill Farms Station, a former dairy farm in rural Virginia that the U. S. Army had bought for $127,500 in June 1942. Near lunchtime on November 10, he found a transmission repeating itself on a German channel: an urgent message from Berlin calling Tokyo.
He stayed at the set through his meal, and the operators who relieved him kept copying the traffic. It ran for two days before it stopped. The man who sent it was Baron Oshima Hiroshi, Japan’s ambassador to Germany. He was not a diplomat by trade.
He was a lieutenant general of the Imperial Japanese Army, the son of a former Army Minister, an artilleryman who had commanded a field regiment and served as military attaché in Berlin since 1934, speaking near-flawless German. By any measure, he was a committed servant of the German cause. After Pearl Harbor, Hitler gave him the Grand Cross of the Order of the German Eagle in gold, one of only fifteen men to receive it. What mattered to the listeners in Virginia was not his politics but his profession.
When the German army showed this man a fortification, he understood what he was looking at, and afterward he wrote it up the way a staff officer writes things up. He also had no other way to file his reports. Until the summer of 1941, the Japanese embassy in Berlin could send heavy material overland by courier along the Trans-Siberian Railway. Germany invaded the Soviet Union on June 22, 1941, sealing that line.
For a man in Berlin with a great deal to say and eight thousand miles to say it across, the consequence was that almost everything now went into the air. Plenty had already gone into it. On June 3, 1941, more than two weeks before the invasion of Russia, Hitler told him that war with the Soviets was in all probability unavoidable, and Oshima passed that to Tokyo. In the summer of 1943, he reported that the U-boats had been ordered to give up their group attacks on convoys, the single piece of news the Admiralty in London most wanted confirmed.
That August, he reported that German aircraft production was being reordered to put fighters ahead of bombers. He described Allied bombing damage to German cities in the flat inventory style of a man counting damage rather than mourning it. In the last week of October 1943, the German command in the West took him to the Atlantic coast. He went out from Paris with several aides and a party of escorts, working his way along the front from Brest down to Bordeaux over roughly nine days.
They toured defensive positions, watched maneuvers and night firing practice, and talked to the troops manning the works. Senior officers explained how the forces in the West were organized and what they would do when the invasion came. When they were wined and dined, he wrote, they always had the chance to talk with the right people. Back in Berlin, he wrote the trip up and sent it to Tokyo in three parts.
It gave the location of every division on that coast with its strength and its weapons. It gave the composition and condition of the mobile reserve. It described the layout of strong points, the calibers of the turrets close to the water, the materials the works were built from, the tank ditches, and the obstacles planted below the tide line to tear the bottoms out of landing craft. It set out the operational concept in plain language: the defenders meant to break an invasion at the waterline.
Then it did something more useful still. It said where the German command thought the blow was coming. The priority in the West was the Pas-de-Calais, two hundred miles up the coast from Normandy, and it was going to stay the Pas-de-Calais. Oshima also passed on what his hosts had not meant to see written down.
Some reserve divisions had been stripped to feed the Russian front. What remained was under strength and short of training. The first intercepts reached Arlington Hall, the girls’ school outside Washington that the Army had taken over as its code-breaking headquarters, on the evening of November 11. What happened to them there took a month.
The cipher, which the Japanese foreign ministry had introduced in 1938, was considered beyond analysis. American cryptanalysts solved it in the autumn of 1940 without ever seeing one of the machines, building instead an analog device of telephone stepping switches that replicated the logic underneath. The text came out as romanized Japanese, because the writing system could not be sent in Morse, and then it had to become English in the hands of young men who had been studying the language for about a year. One of them was a twenty-year-old from Queens named Bernard Weisberger, pulled out of Columbia, run through eight weeks of concentrated language study, and turned into a private in the Second Signal Service Battalion.
He described the transition without much ceremony. One morning he was a student; the next morning he was reading a report from the ambassador in Berlin that was less than forty-eight hours old. The English those translators produced was accurate and not readable. Screeners in the Pentagon took the decrypted messages as they came in and sent each one to the area desk covering its subject, each carrying a single word of instruction: note or write.
A message marked note went to the desk officer to read and then into a file, because many of these messages made sense only against those that had come before. A message marked write went to the desk officer to be rebuilt into something a busy man could take in on one pass. For the Oshima trip report, they went further than usual, supplying the real names of the German generals he had met, removing honorifics, and paraphrasing the ambassador outright. On December 14, a lieutenant colonel at the Signal Security Agency sent the package forward.
On December 16, it was on the president’s desk. The full text was not finished in translation until December 11, though a draft reached General Marshall and the White House within a day of the intercept. What never varies across the accounts is the part that mattered to the men planning the invasion of Europe: the divisions, the fortifications, and the Pas-de-Calais. Oshima answered the obvious question himself fourteen years later.
In November 1959, sitting for interviews with military historians in Tokyo, he was asked about the security of his transmissions. He said that in 1941, a German diplomat had warned him there were indications the Allies were reading Japanese diplomatic traffic. The Germans raised the subject more than once over the years, and each time Oshima assured them the system was sound. He had taken his own precaution.
He double enciphered his dispatches, and he was satisfied that nothing enciphered twice could be read by anybody. The cipher stayed in service until the end of the war. On the day of Pearl Harbor, 105 civilians handled the intercept traffic that the Americans called Magic. By February 1943, Arlington Hall had close to seventeen times that number, and by the end of the war, better than ten thousand, about seven thousand of them women.
Approximately seventy of Oshima’s own messages went out over the last eleven months of 1941. Two years later, the annual figure stood at four hundred. In 1944, it reached half again as many, and across the four months of war Germany had left in 1945, his traffic still ran at better than seventy messages a month. None of it was worth anything until it reached a man who could act on it.
The summaries went to the White House and were handed to the president’s naval aide, and once Roosevelt had read them, a courier destroyed the paper. From the start of 1944, the chief of staff had his own copies bound each day into a black book for his morning meeting. Field commanders were kept outside the circle, because every additional reader multiplied the chance that somebody would act on the material in a way that told the enemy where it came from. Eisenhower himself was not brought inside until late June 1942.
The solution was a system of special security officers, the first group of twenty trained in July 1943 and sent out to theater headquarters in September. Each carried his own cipher equipment, deciphered the incoming traffic himself, walked it into the commander’s office, and kept custody of every sheet until it was destroyed. On June 1, 1944, five days before the landings, Oshima cabled Tokyo an account of what Hitler expected. The Führer anticipated diversionary attacks in Norway, Denmark, and on the French Mediterranean coast and believed the real assault would come across the Strait of Dover into the Pas-de-Calais.
Every fictitious division the Allies had invented in Southeast England, every rubber tank and false radio net, stood confirmed as working by the man it was all aimed at, in his own words, read in Virginia. In September 1944, George Marshall put it in one line when writing to Governor Thomas Dewey: Baron Oshima’s messages from Berlin were the main basis of information regarding Hitler’s intentions in Europe. None of it made the picture complete, and one stretch of coast proved it. The Allied estimate for the sector the Americans called Omaha had the beach held by a reinforced battalion of a static division thought to be half filled with men who were not German.
A full-strength division with combat experience, the 352nd Infantry Division, sat in that estimate about twenty miles inland, where it would come up for a counterattack later in the day. The 352nd had been ordered forward to the coast in March in the spirit of the doctrine Oshima had written down for Tokyo, and the move went unnoticed. The first waves at Omaha came ashore in front of a division nobody had briefed them on. Almost none of the people who produced the intelligence were ever told what they had produced.
The work was cut into pieces on purpose. Ann Caracristi, who spent the war at Arlington Hall and later became the first woman to serve as deputy director of the National Security Agency, described it afterward as an assembly line, everyone working a small portion of something with next to no feedback about what any finished product had done. Weisberger, who at least knew whose reports he was translating, wrote that it was a thrill that could not be shared. Some left almost no record at all.
William Coffee joined the Signal Intelligence Service as a janitor, moved up to messenger, and in early 1944 took on the job of building the first all-black unit at Arlington Hall. The unit took over commercial coded traffic and did real analytical work, and in April 1946 Coffee received a commendation for meritorious civilian service. Then the story went quiet for fifty years. On February 20, 1948, Omar Bradley, by then Army Chief of Staff, drove out to Vint Hill Farms Station, ate lunch with the people who worked there, and thanked them for the information from the Japanese intercepts.
He thanked them, in his words, for serving so silently and yet so magnificently. That was as close as most of them came to a citation. In Berlin at the end, the embassy staff took the cipher machine apart and buried the pieces in the air raid shelter. American teams dug the fragments out after the surrender, and the largest surviving piece of the machine that carried the Atlantic Wall to Washington sits today in a display case at the National Cryptologic Museum in Maryland.
Oshima left Berlin on Hitler’s order in April 1945, was held briefly by American forces, went home to Japan in November, was arrested by occupation authorities that December, and was convicted by the International Military Tribunal for the Far East of conspiracy to wage aggressive war. He received life imprisonment, came out on parole at the end of 1955, and died in 1975 at the age of eighty-nine. Nothing about the reading of his mail was public until the National Security Agency began releasing the wartime material into the National Archives in the late 1970s.
As the historian Carl Boyd put it after years with the intercepts, Oshima died never knowing that his mail had been read in Washington and London for the whole of the war.