Kinetic or firepower
Beginning with the use of melee and missile weapons such as clubs and spears, the kinetic or firepower function of tactics has developed along with technological advances so that the emphasis has shifted over time from the close-range melee and missile weapons to longer-range projectile weapons. Kinetic effects were generally delivered by the sword, spear, javelin and bow until the introduction of artillery by the Romans. Until the mid 19th century, the value of infantry-delivered missile firepower was not high, meaning that the result of a given battle was rarely decided by infantry firepower alone, often relying on artillery to deliver significant kinetic effects. The development of disciplined volley fire, delivered at close range, began to improve the hitting power of infantry, and compensated in part for the limited range, poor accuracy and low rate of fire of early muskets. Advances in technology, particularly the introduction of the rifled musket, used in the Crimean War and American Civil War, meant flatter trajectories and improved accuracy at greater ranges, along with higher casualties. The resulting increase in defensive firepower meant infantry attacks without artillery support became increasingly difficult. Firepower also became crucial to fixing an enemy in place to allow a decisive strike. Machine guns added significantly to infantry firepower at the turn of the 20th century, and the mobile firepower provided by tanks, self-propelled artillery and military aircraft rose significantly in the century that followed. Along with infantry weapons, tanks and other armoured vehicles, self-propelled artillery, guided weapons and aircraft provide the firepower of modern armies.
Mobility, which determines how quickly a fighting force can move, was for most of human history limited by the speed of a soldier on foot, even when supplies were carried by beasts of burden. With this restriction, most armies could not travel more than 32 kilometres (20 mi) per day, unless travelling on rivers. Only small elements of a force such as cavalry or specially trained light troops could exceed this limit. This restriction on tactical mobility remained until the latter years of World War I when the advent of the tank improved mobility sufficiently to allow decisive tactical manoeuvre. Despite this advance, full tactical mobility was not achieved until World War II when armoured and motorised formations achieved remarkable successes. However, large elements of the armies of World War II remained reliant on horse-drawn transport, which limited tactical mobility within the overall force. Tactical mobility can be limited by the use of field obstacles, often created by military engineers.
Protection and security
Personal armour has been worn since the classical period to provide a measure of individual protection, which was also extended to include barding of the mount. The limitations of armour have always been weight and bulk, and its consequent effects on mobility as well as human and animal endurance. By the 18th and 19th centuries, personal armour had been largely discarded, until the re-introduction of helmets during World War I in response to the firepower of artillery. Armoured fighting vehicles proliferated during World War II, and after that war, body armour returned for the infantry, particularly in Western armies. Fortifications, which have been used since ancient times, provide collective protection, and modern examples include entrenchments, roadblocks, barbed wire and minefields. Like obstacles, fortifications are often created by military engineers.
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 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.