Chemical weapons in the Rif War During the Third Rif War in Spanish Morocco between 1921 and 1927 , the Spanish Army of Africa dropped chemical warfare agent s in an attempt to put down the Rif fian Berber rebellion led by guerrilla leader Abd el - Krim . These attacks in 1924 marked the second confirmed case of mustard gas being dropped from airplanes , a year before the signing of the Geneva Protocol for " the Prohibition of the Use in War of Asphyxiating , Poisonous or other Gases , and of Bacteriological Methods of Warfare " . The gas used in these attacks was produced by the " Fabrica Nacional de Productos Quimicos " at La Marañosa near Madrid ; a plant founded with significant assistance from Hugo Stoltzenberg , a chemist associated with the German government ' s clandestine chemical warfare activities in the early 1920s who was later given Spanish citizenship . Researches and revelations . The Spanish bombings were covered up but some observers of military aviation , like Pedro Tonda Bueno in his autobiography " La vida y yo " ( " Life and I " ) , published in 1974 , talked about dropping toxic gases from airplanes and the consequent poisoning of the Rif fields . Likewise , Spanish Army air arm pilot Ignacio Hidalgo de Cisneros , in his autobiographical work " Cambio de rumbo " ( " Course change " ) , reveals how he witnessed several chemical attacks . Years later , in 1990 , two German journalists and investigators , Rudibert Kunz and Rolf - Dieter Müller , in their work " Giftgas Gegen Abd El Krim : Deutschland , Spanien und der Gaskrieg in Spanisch - Marokko , 1922 - 1927 " ( " Poison Gas against Abd El Krim : Germany , Spain and the Gas War in Spanish Morocco , 1922 - 1927 " ) , proved with scientific tests that chemical attacks had indeed occurred . The British historian Sebastian Balfour , of the London School of Economics , in his book " Deadly Embrace " , confirmed massive use of chemical arms after having studied numerous Spanish , French and British archives . According to his research , the strategy of the Spanish military was to choose highly populated zones as targets . Additional evidence is found in a telegram from a British official , H . Pughe Lloyd , sent to the British Minister of War . Background . According to Sebastian Balfour , the motivation for the chemical attacks was based primarily on revenge for the defeat of the Spanish Army of Africa and their Moroccan recruits the Regulares at the Battle of Annual on July 22 , 1921 . The Spanish defeat , the disaster of Annual , with 13 , 000 Spanish and colonial soldiers dead according to the official count , led to a major political crisis and a redefinition of Spanish colonial policy toward the Rif region . The political crisis led Indalecio Prieto to say in the Congress of Deputies : " We are at the most acute period of Spanish decadence . The campaign in Africa is a total failure , absolute , without extenuation , of the Spanish Army . " The Minister of War ordered the creation of an investigative commission , directed by the respected general Juan Picasso González , which eventually developed the " Expediente Picasso " report . Despite identifying numerous military mistakes , it did not , owing to obstructions raised by various ministers and judges , go so far as to lay political responsibility for the defeat . Popular opinion widely blamed King Alfonso XIII who , according to several sources , encouraged General Manuel Fernández Silvestre ' s irresponsible penetration of positions far from Melilla without having adequate defenses in his rear . Even before the use of chemical weapons , the Spanish Army commonly resorted to brutal methods of repression , which in some cases included decapitation , after its initial defeats in the Second Rif War of 1909 . The use of the chemical agents . Spain was one of the first powers to use chemical weapons against civilian populaces in their use against the Rif rebellion . Between 1921 and 1927 , the Spanish army indiscriminately used phosgene , diphosgene , chloropicrin and mustard gas ( known as " Iperita " ) . Common targets were civilian populations , markets , and rivers . In a telegram sent by the High Commissioner of Spanish Morocco Dámaso Berenguer on August 12 , 1921 to the Spanish minister of War , Berenguer stated : On August 20 , 1921 , Spain asked Germany to deliver mustard gas via Hugo Stoltzenberg , although Germany was prohibited from manufacturing such weapons by the Treaty of Versailles of 1919 . The first delivery occurred in 1923 . The use of chemical weapons against the Rif was first described in an article of a ( now defunct ) Francophone daily newspaper published in Tangier called " La Dépêche marocaine " dated on November 27 , 1921 . Historian Juan Pando has been the only Spanish historian to have confirmed the usage of mustard gas starting in 1923 . Spanish newspaper " La Correspondencia de España " published an article called " Cartas de un soldado " ( " Letters of a soldier " ) on August 16 , 1923 which backed the usage of mustard gas . According to military aviation general Hidalgo de Cisneros in his autobiographical book " Cambio de rumbo " , he was the first warfighter to drop a 100 - kilogram mustard gas bomb from his Farman F60 Goliath aircraft in the summer of 1924 . About 127 fighters and bombers flew in the campaign , dropping around 1 , 680 bombs each day . Thirteen of these planes were stationed in the military air base of Seville . The mustard gas bombs were brought from the stockpiles of Germany and delivered to Melilla before being carried on Farman F60 Goliath airplanes . Legacy . Alleged toxic effects . The Association for the Defence of Victims of the Rif War considers that the toxic effects are still being felt in the Rif region . However , no scientific study has proven to date the relationship between the usage of chemical weapons and the high rate of cancer in the area . Bill of acknowledgment . On February 14 , 2007 , the Catalonian party of the Republican Left ( Esquerra Republicana de Catalunya ) passed a bill to the Spanish Congress of Deputies requesting Spain to acknowledge the " systematic " use of chemical weapons against the population of the Rif mountains . The bill was rejected by 33 votes from the governing Socialist Labor Party and the opposition right - wing Popular Party who form the majority in the Spanish parliament .