Beginning in October 1935 and continuing into the following months Fascist Italy used mustard gas against the Ethiopians during the Second Italo-Abyssinian War in violation of the Geneva Protocol. Italian general Rodolfo Graziani first ordered the use of chemical weapons at Gorrahei against the forces of Ras Nasibu .  Benito Mussolini personally authorized Graziani to use chemical weapons.  Chemical weapons dropped by warplane "proved to be very effective" and was used "on a massive scale against civilians and troops, as well as to contaminate fields and water supplies."  Among the most intense chemical bombardment by the Italian Air Force in Ethiopia occurred in February and March 1936, although "gas warfare continued, with varying intensity, until March 1939."  J. F. C. Fuller , who was present in Ethiopia during the conflict, stated that mustard gas "was the decisive tactical factor in the war."  Some estimate that up to one-third of Ethiopian casualties of the war were caused by chemical weapons.