Chemical weapons: Spain
In addition to being the first use of toxic gas dropped from planes, Spain was also one of the first instances of toxic gas being used against civilian population. The Spanish military was specifically instructed to attack population centers, hoping to break the will of sympathetic civilians. The gas-bombs were dropped from Farman F.60 Goliath heavy bomber, shown below, built under licence in Spain. The gases used were purchased from Germany via German chemist Hugo Stoltzenberg, a leading figure in Germany's secret gas development and research, as the treaty of Versailles prohibited Germany from producing any chemical agents.