Leaflet propaganda dropped by balloons and planes was used heavily in both world wars by all sides. In World War II, special bombs were developed to disperse airborne leaflets. Used as a form of psychological warfare, these leaflets were dropped in enemy-controlled territory to incite fear, coerce surrender, or turn the populace against their leadership. This tactic proved to be largely ineffective, except when morale among troops was extremely low. Leaflet bombs are still used today in military warfare, as well as by radical political and ideological groups.