 He was sent as a military attaché to the United Kingdom in November 1911 and to British India in July 1913. he returned to Japan briefly in January 1916, was promoted to major in May and sent back to Europe in August as a military observer embedded with the Royal Army on the front lines during World War I.He returned to Japan in March 1918, and was private secretary to Army Minister Ōshima Ken'ichi from July 1918 to July 1919, when was promoted to lieutenant colonel.Tatekawa was assigned as the official Imperial Japanese Army representative to the Japanese delegation at the League of Nations between July 1920 and December 1922.