Infantry

Infantrymen of the US 6th Marine Division search the ruins of Naha, Okinawa for Japanese snipers, Spring 1945
Infantry of the Royal Irish Rifles at the Battle of the Somme (July–November 1916) during the First World War

Infantry is the branch of an army that engages in military combat on foot, distinguished from cavalry, artillery, and tank forces. Also known as foot soldiers, infantry traditionally relies on moving by foot between combats as well, but may also use mounts, military vehicles, or other transport. Infantry make up a large portion of all armed forces in most nations, and typically bear the largest brunt in warfare, as measured by casualties, deprivation, or physical and psychological stress.

The first military forces in history were infantry. In antiquity, infantry were armed with an early melee weapon such as a spear, axe or sword, or an early ranged weapon like a javelin, sling, or bow, with a few infantrymen having both a melee and a ranged weapon. With the development of gunpowder, infantry began converting to primarily firearms. By the time of Napoleonic warfare, infantry, cavalry, and artillery formed a basic triad of ground forces, though infantry usually remained the most numerous. With armoured warfare, armoured fighting vehicles have replaced the horses of cavalry, and airpower has added a new dimension to ground combat, but infantry remains pivotal to all modern combined arms operations.

Infantry have much greater local situational awareness than other military forces, due to their inherent intimate contact with the battlefield ("boots on the ground"); this is vital for taking or holding ground (any military objectives), securing battlefield victories, maintaining military area control and security both at and behind the front lines, for capturing ordnance or materiel, taking prisoners, and military occupation. Infantry can more easily recognise, adapt and respond to local conditions, weather, and changing enemy weapons or tactics. They can operate in a wide range of terrain inaccessible to military vehicles, and can operate with a lower logistical burden. Infantry are most easily deliverable forces to ground combat areas, by simple and reliable marching, or by trucks, sea or air transport; they can also be inserted directly into combat by amphibious landing, or for air assault by parachute or helicopter ("airmobile" or "airborne" infantry). They can be augmented with a variety of crew-served weapons and armoured personnel carriers.

Etymology and terminology

Various infantry of the 17th through 18th century (halberdier, arquebusier, pikeman, and mix of musketeers and grenadiers) of Duchy of Württemberg
Infantry of the US 3rd Armored Cavalry Regiment enter their M2 Bradley IFV during a combat patrol, Tall Afar, Iraq, 2006

In English, use of the term infantry began about the 1570s, describing soldiers who march and fight on foot. The word derives from Middle French infanterie, from older Italian (also Spanish) infanteria (foot soldiers too inexperienced for cavalry), from Latin īnfāns (without speech, newborn, foolish), from which English also gets infant.[1] The individual-soldier term infantryman was not coined until 1837.[2] In modern usage, foot soldiers of any era are now considered infantry and infantrymen.[3]

From the mid-18th century until 1881 the British Army named its infantry as numbered regiments "of Foot" to distinguish them from cavalry and dragoon regiments (see List of Regiments of Foot).

Infantry equipped with special weapons were often named after that weapon, such as grenadiers for their grenades, or fusiliers for their fusils.[note 1] These names can persist long after the weapon speciality; examples of infantry units that retained such names are the Royal Irish Fusiliers and the Grenadier Guards.

More commonly in modern times, infantry with special tactics are named for their roles, such as commandos, rangers, snipers, marines, (who all have additional training) and militia (who have reduced training); they are still infantry due to their expectation to fight as infantry when they enter combat.

Dragoons were created as mounted infantry, with horses for travel between battles; they were still considered infantry since they dismounted before combat. However, if light cavalry was lacking in an army, any available dragoons might be assigned their duties; this practise increased over time, and dragoons eventually received all the weapons and training as both infantry and cavalry, and could be classified as both. Conversely, starting about the mid-19th century, regular cavalry have been forced to spend more of their time dismounted in combat due to the ever-increasing effectiveness of enemy infantry firearms. Thus most cavalry transitioned to mounted infantry. As with grenadiers, the dragoon and cavalry designations can be retained long after their horses, such as in the Royal Dragoon Guards, Royal Lancers, and King's Royal Hussars.

Similarly, motorised infantry have trucks and other unarmed vehicles for non-combat movement, but are still infantry since they leave their vehicles for any combat. Most modern infantry have vehicle transport, to the point where infantry being motorised is generally assumed, and the few exceptions might be identified as modern light infantry, or "leg infantry" colloquially. Mechanised infantry go beyond motorised, having transport vehicles with combat abilities, armoured personnel carriers (APCs), providing at least some options for combat without leaving their vehicles. In modern infantry, some APCs have evolved to be infantry fighting vehicles (IFVs), which are transport vehicles with more substantial combat abilities, approaching those of light tanks. Some well-equipped mechanised infantry can be designated as armoured infantry. Given that infantry forces typically also have some tanks, and given that most armoured forces have more mechanised infantry units than tank units in their organisation, the distinction between mechanised infantry and armour forces has blurred.

The terms "infantry", "armour", and "cavalry" used in the official names for military units like divisions, brigades, or regiments might be better understood as a description of their expected balance of defensive, offensive, and mobility roles, rather than just use of vehicles. Some modern mechanised infantry units are termed cavalry or armoured cavalry, even though they never had horses, to emphasise their combat mobility.

In the modern US Army, about 15% of soldiers are officially Infantry.[4] The basic training for all new US Army soldiers includes use of infantry weapons and tactics, even for tank crews, artillery crews, and base and logistical personnel.