 Japan also used poison gas against Chinese Muslim armies at the Battle of Wuyuan and Battle of West Suiyuan.Despite Article 23 of the Hague Conventions of 1899 and 1907, article V of the Treaty in Relation to the Use of Submarines and Noxious Gases in Warfare, article 171 of the Treaty of Versailles
and a resolution adopted by the League of Nations on May 14, 1938, condemning the use of poison gas by the Empire of Japan, the Imperial Japanese Army frequently used chemical weapons during the war.According to historians Yoshiaki Yoshimi and Seiya Matsuno, the chemical weapons were authorized by specific orders given by Japanese Emperor Hirohito himself, transmitted by the Imperial General Headquarters.