Leaflets in war are a form of psychological warfare used to incite fear, coerce surrender, or turn the populace against their leadership. They are dropped in enemy-controlled territory by balloons, planes, or shells. Leaflets were first used on a large scale during World War I by all parties, and the British dropped packets of leaflets over Imperial German Army trenches containing postcards from prisoners of war detailing their humane conditions, surrender notices, and general propaganda against Kaiser Wilhelm II and the German generals. During World War II, special bombs were developed to disperse airborne leaflets. Although leaflets were seen as effective in manipulating troops when morale was low, they were not effective when distributing surrender leaflets to an enemy with high morale among its troops. Leaflet bombs are still used today in military warfare, as well as by radical political and ideological groups.