• Kyodo

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The Soviet Union deciphered a coded telegram from the Foreign Ministry to the Japanese ambassador in Germany expressing Japan’s intention to go to war with the United States, according to declassified documents of the NKVD, the forerunner of the KGB, made available Monday.

The documents represent the first hard evidence that the Soviet Union succeeded in deciphering Japan’s coded messages before the launch of the Pacific War in December 1941. It was already known the United States succeeded in deciphering the messages.

The latest finding shows that Japan went to war unaware that both the Soviet Union and the United States knew of its intention to launch hostilities beforehand.

According to the documents, the NKVD deciphered a confidential telegram sent by the Foreign Ministry to Ambassador Hiroshi Oshima in Berlin after Nov. 20, 1941.

In the telegram, the ministry instructed Oshima to explain secretly to Adolf Hitler and Foreign Minister Joachim von Ribbentrop that Japan-U.S. negotiations were in a stalemate and that Japan might go to war against Britain and the United States much earlier than it had expected.

The United States deciphered the telegram Dec. 1, 1941, a week before Japan’s attack on Pearl Harbor, but the Soviet Union might have had decoded it before Washington because one of the declassified documents was dated Nov. 27.

The information contained in the telegram is believed to have been extremely valuable to the Soviet Union, which was already at war with Germany and wanted to avoid confronting Germany and Japan at the same time. The telegram instructed Oshima to convey to Hitler Japan’s intention to deploy its forces mainly in Southeast Asia and the Pacific.