On February 8, 1904, Japan went to war with Russia in Manchuria. By this time, an extensive intelligence network had been established that provided accurate intelligence on the locations and strengths of enemy forces. The Japanese navy launched a surprise attack on Port Arthur in China--Russia had leased Port Arthur from China in 1898—and blockaded the damaged Russian vessels. Russia decided to send its Baltic Fleet, consisting of 45 ships, to try to break the blockade.
Fishermen Spies
Disguised as fishermen aboard fishing vessels, Japanese agents monitored the voyage of the Baltic Fleet. Admiral Heihachiro Togo, commander of the Japanese battle fleet, intercepted the Russian vessels in the Straits of Tsushima on May 27, 1905. Worn out by the long, arduous passage from Europe, the Russian ships were at the mercy of the Japanese fleet’s superior speed and armaments and when the smoke cleared, Russian fatalities totaled 4,000, while the Japanese had lost 116 men. The Russians accepted defeat and evacuated Manchuria.
Captain Malcolm D. Kennedy, a former British military attaché and Reuters correspondent based in Tokyo, wrote in his The Military Side of Japanese Life, “One of the great features of Japanese strategy and grand tactics in their war with Russia was the secrecy observed and the false information circulated purposely. This, combined with their system of intelligence work, which both before that war and during it, enabled them to have an almost uncanny knowledge of their enemy’s doings and potentialities, helped them very considerably to subsequent victory.”
Following Russia’s defeat, Japan’s role in international affairs was changed forever. The war marked the first time an Asian power had defeated a European power in modern times. It was not the last time Japan would become involved in Manchuria.
World War I
When World War I broke out, Japan sent an ultimatum to Germany demanding the immediate evacuation of the German-leased territory of Jiaozhou in northeastern China. Japan entered the war on the side of the Allies when Germany refused to comply with the ultimatum. Japan’s task was to monitor activity in the various German colonies of the Pacific, and Japanese forces eventually occupied the Marshall, Caroline, and Mariana Islands in the Pacific. The occupation of these islands provided the Japanese with air and seabases from which they could spy on shipping lanes across the Pacific Ocean, and would later provide important bases for Pacific Theater operations during World War II.
For a look at Japanese intelligence prior to the Russo-Japanese War, read "Japanese Intelligence: Origins of Japan's Espionage Activities" and " Japanese Intelligence in the Early 20th Century: The Black Dragon Society."