Spanish use of chemical weapons in the Rif War

During the Third Rif War in Spanish Morocco between 1921 and 1927, the Spanish Army of Africa deployed chemical weapons in an attempt to put down the Berber rebellion against colonial rule in the region of the Rif led by the guerrilla Abd el-Krim. In 1921, following the Rifian victory in the Battle of Annual, which was considered the worst Spanish military defeat of modern history, the Spanish army pursued a campaign of retribution involving the indiscriminate and routine dropping of toxic gas bombs targeting civilian populations, markets and rivers.

Source: Wikipedia — Spanish use of chemical weapons in the Rif War (CC BY-SA 4.0)