Shock action is as much a psychological function of tactics as a physical one, and can be significantly enhanced by the use of surprise. It has been provided by charging infantry, and as well as by chariots, war elephants, cavalry and armoured vehicles which provide momentum to an assault. It has also been used in a defensive way, for example by the drenching flights of arrows from English longbowmen at the Battle of Agincourt in 1415 which caused the horses of the French knights to panic. During early modern warfare, the use of the tactical formations of columns and lines had a greater effect than the firepower of the formations alone. During the early stages of World War II, the combined effects of German machine gun and tank gun firepower, enhanced by accurate indirect fire and air attack, often broke up Allied units before their assault commenced, or caused them to falter due to casualties among key unit leaders. In both the early modern and World War II examples, the cumulative psychological shock effect on the enemy was often greater than the actual casualties incurred.
