SSA Sends Trip Report to FDR (14 DEC 1943)

Photo By Erin Thompson | Baron Oshima inspecting parts of the German Atlantic Wall in November 1943  

UNITED STATES

12.08.2023

Courtesy Story

U.S. Army Intelligence Center of Excellence

by Michael E. Bigelow, INSCOM Command Historian

SSA SENDS TRIP REPORT TO FDR
On 14 December 1943, Lt. Col. Earle F. Cook of the Signal Security Agency (SSA) used channels to forward a series of intercepted messages to President Franklin D. Roosevelt. Two days later, the messages, containing a revealing look at German coastal defenses, were in the hands of the President.

In these messages, Baron Oshima Hiroshi, the Japanese ambassador to Germany, described his nine-day tour of the German defenses along the French coast. Oshima, a former Japanese Army general, was an astute observer and his report described the defenses with military precision and detail. In early November, he sent his report back to Tokyo in a series of three messages. Unfortunately for Oshima, the messages used the diplomatic code PURPLE that the American cryptanalysts had been reading since the fall of 1940. [See "This Week in MI History" #204 20 September 1940] By the evening of 11 November, intercepted transmissions of the messages started to reach the SSA headquarters at Arlington Hall, near Washington, D.C.

As parts of Oshima’s report flowed in, the SSA reconstructed the report. It revealed that Oshima and several aides, with their German escorts, had traveled from Paris to the French coast from Brest to Bordeaux, inspecting fortifications along the Atlantic coast. From 24 October to 1 November 1943, they had toured defensive positions, watched maneuvers, night firing practice, and talked to German soldiers. Senior German officers briefed Oshima on the organization of their forces and how they planned to use them. “When we were wined and dined,” Oshima noted, “we always had the chance to talk with the right people—those who could answer our questions.”

The analysts from both the SSA and Army G-2 soon realized they had an informative report that provided an excellent overview of the enemy forces in France. It gave the composition and disposition of German forces, a tactical layout of the fortifications, and the German military’s operational concepts. This proved to be a windfall since the Anglo-American planners had just begun its next round of planning for the Allied invasion of France. With Baron Oshima’s keen eye for military detail, his report served as an effective framework to update, revise, or confirm estimates for Operation OVERLORD, the planned Normandy landings.

Most important for the Allied planners, Oshima confirmed the German priority in defending the Pas-de-Calais, about two hundred miles to the northeast of Normandy. In addition, he laid out the German defensive strategy. “It is quite clear,” he pointed out, “that the Germans plan to smash any enemy attempt to as close to the edge of the water as possible.” He went on to postulate that “Were [the Allies] successful in making a partial landing, crossfire from mutually supporting defense posts and the appearance of mobile forces would annihilate the invaders.” At the same time, he pointed out the condition of these reserve forces. Some had recently been sent to the Russian front and those that remained were understrength and in need of training. Moreover, Oshima’s information on the numbers and status of the German divisions gave grist for the Allied order of battle analysts. Finally, his details on weapons calibers, construction materials, and strongpoint layout provided useful information to the Allied planners.

Before reaching the President, Colonel Cook and the SSA prepared the report for the chief executive. Analysts provided full names for the German generals who had met with Oshima. Also, they often had to change a phonetic spelling to the proper one: so General “Tsuootenshutain” became General von Sodenstern and Admiral “Kuranke” became Admiral Krancke. Translators and editors smoothed over the language so “nests of resistance” became strongpoints and unnecessary German titles were omitted. Sometimes they paraphrased the Japanese ambassador. With the revisions made, on 16 December, President Roosevelt was able to read what one historian called “the blueprint to Hitler’s fortifications along the northern French coast.”

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• Date Taken: 12.08.2023
• Date Posted: 12.08.2023 15:02
• Story ID: 459532
• Location: US