 Okamura was promoted to lieutenant general in 1936, and assigned command of the IJA 2nd Division.In 1938, a year after the Marco Polo Bridge Incident, Okamura was assigned as the commander in chief of the Japanese Eleventh Army, which participated in numerous major engagements in the Second Sino-Japanese War, notably the Battles of Wuhan, Nanchang and Changsha.According to historians Yoshiaki Yoshimi and Seiya Matsuno, Okamura was authorized by Emperor Hirohito to use chemical weapons during those battles.