Complex sentence: Doihara's performance was recognized, and he was assigned to Imperial Japanese Army General Staff in 1930 to 1931, and assigned to head military espionage operations from the Army's Tientsin office.
Split into simpler sentences: Doihara's performance was recognized, and he was assigned to Imperial Japanese Army General Staff in 1930. He headed military espionage operations from the Army's Tientsin office.