Sawada was the third son of a farmer in what is now the Kamobe neighborhood of the city of Kochi, Kōchi Prefecture. After attending military preparatory schools in Kōchi and Hiroshima, he graduated from the 18th class of the Imperial Japanese Army Academy in 1905, serving as a junior officer in an artillery regiment. In 1910, he was sent to the Artillery Engineering School, and to the 26th class of the Army War College in 1914. On graduation, he was assigned to the Record and Documentation Bureau of Imperial Japanese Army General Staff, where he was assigned to the task of compiling an official record of the Russo-Japanese War. In January 1918, while still under the General Staff Office, he was assigned to accompany Japanese forces in the Japanese intervention in Siberia, and was assigned to the staff at Vladivostok and Omsk. Already fluent in the French language, he also studied then Russian language, until he was forced to return to Japan due to typhus in February 1921. In November 1922, despite being an expert in Soviet affairs, he was assigned as a military attache to Greece. In August 1926, he was promoted to lieutenant colonel and served as an instructor at the Army Staff College. he became director of the Harbin Special Agency from November 1928. In October 1930, he was promoted to colonel.