Infantry of the Royal Irish Rifles during the Battle of the Somme in World War I.
Infantry of the Royal Irish Rifles during the Battle of the Somme in World War I.

Infantry is a term for soldiers who fight primarily on foot with small arms in organized military units. It may also be more broadly assigned as a blanket term for larger military organizational structures consisting of units whose focus is deploying infantrymen but also contain large numbers of soldiers in supporting roles (for example, an Infantry Regiment may have only a minority of its soldiers actively engaged in fighting the enemy on foot.) These broad categorizations may also include a defined role related to their equipment or method of transport (for example, Parachute Infantry, Mountain Infantry, Mechanized Infantry, etc.)


With few exceptions, most armies in history have been built around a core of infantry. While the specific weapons have varied, the common factor is that these soldiers have relied on their feet for operational movements (transportation behind the lines, especially in the pre-industrial era) and tactical movement (movement in battle) although they may sometimes be transported to the battlefield by various means.

In earliest days, infantry were essentially armed mobs, fighting in loosely organized opposing lines under the voice direction of individual commanders in the immediate vicinity (within earshot) of the troops under their command. However, the benefits of uniform equipment, weaponry and above all training led to the development of formations able to carry out pre-arranged tactical maneuvers in the heat of battle.

Infantry organization has focused since recorded history began on striking a balance between heavily-armed formations (such as the Greek phalanx) fighting in rigid formations, and more lightly-armed but more mobile units (like the Roman legion) able to move relatively quickly around the battlefield and exploit opportunities as they arose. Mobility, weaponry, and protection have been the competing yet complementary factors to be balanced.

Classical Period

Examples of infantry units of the Classical period are the phalanxes of ancient Greece and the legions of Imperial Rome. In contrast to the strictly organized phalanxes and legions, most armies of the ancient world also employed units of skirmishers (often mercenaries or slaves) who wore minimal armor and carried an eclectic mix of weapons ranging from swords and javelins to slings and bows. Infantry was the primary combat arm of the period in open battles, as a result of multiple factors, including the cultural bias toward hand-to-hand combat and the relatively limited effectiveness of ranged weapons. Ranged weapons were primarily used as artillery and siege weapons. Classical cavalry was considered largely ineffective for anything but harassment, largely due to the fact that stirrups had yet to be brought to Europe.

Large, well-disciplined units of infantry were common to the wars of the ancient world. However, as the Roman Empire declined and fell to the depredations of Germanic tribes such as the Vandals, Goths, and Visigoths in the 5th century AD, the political and military resources necessary for the maintenance of such units largely disappeared until the later Middle Ages with the appearance of the large bureaucratic systems associated with the monarchical nation-states.

Middle Ages

For most of the Middle Ages, warfare and society were dominated by the cavalry (horse-mounted soldiers), composed of individual knights. Knights were generally drawn from the aristocracy, while the infantry levies were raised from commoners. This situation slowed the advance of infantry tactics and weapon technologies; those that were developed by the end of the Middle Ages included the use of long spears or halberds to counter the long reach of knights' lances, and the increased use of ranged weaponry to counter the cavalry's advantages of momentum, speed, height, and reach.

Austrian infantry wearing bicornes and carrying muskets.
Austrian infantry wearing bicornes and carrying muskets.

While bows remained in use long after the development of firearms, technological fine-tuning (along with the development of the wheel-lock) allowed firearms to supersede even the feared English longbow as the ranged weapon of choice for infantry. The bow also declined in favor due to the ease with which musketeers could be trained (days or weeks to attain moderate proficiency, as opposed to many years for the longbow).

Many nations combined firearms with extremely long pikes into units that were virtually invincible against cavalry formations. Eventually, with the development of the bayonet, the pikemen were dropped from the formation, resulting in the first examples of an infantry unit as recognizable today.


Before the development of railroads in the 19th century, infantry armies got to the battlefield by walking, or sometimes by ship. The Marines were first conceived in the 16th century by the Spanish (Infanteria de Marina), followed in the 17th century by other European countries including the United Kingdom. Due to Britain's island status, a large army was unnecessary, however infantry soldiers were still required for eventual landings. A typical Royal Navy warship carried 600 men. Of these men, 120-180 would be Royal Marines. These men usually had a deck to themselves and had little to do with sailing the vessel. The men were proficient in the use of metal-working, gunpowder and modern weapons of the day and would form landing parties when exploring. The Marines also defended the vessel if boarded and would repair damaged weapons and cannons after a battle.

In the 1890s and later, some countries used bicycle infantry, but the real revolution in mobility started in the 1920s with the use of motor vehicles, resulting in motorized infantry. Action in World War II demonstrated the importance of protecting the soldiers while they are moving around, resulting in the development of mechanized infantry, who use armored vehicles for transport. World War II also saw the first widespread use of paratroops, which played key roles in several campaigns in the European theater. During the Vietnam conflict, the United States Army pioneered the use of helicopters to deliver large numbers of infantry quickly to and from key locations on the battlefield. These formations are known as airmobile.

Modern-day mechanized infantry is supported by armored fighting vehicles, artillery, and aircraft, but along with light infantry, which does not use armored fighting vehicles, is still the only kind of military force that can take and hold ground, and thus remains essential to fighting wars. However, the tactic of having massive formations of infantry on open terrain fight it out has fallen into disuse ever since World War II. This is mainly because of advanced technology which can support, replace, and exceed the capabilities of infantry. Modern politics have also to some extent kept the practice of total war and mass combat to a minimum.


Historical recreation of infantry in a military camp
Historical recreation of infantry in a military camp

Infantry is notable by its reliance on organized formations to be employed in battle. These have been developed over time, but remain a key element to effective infantry development and deployment. Up until the 20th Century, infantry units were for the most part employed in close organized formations up until the last moment possible. This was necessary to allow commanders to retain control of the unit, especially while maneuvering, as well as allowing officers to retain discipline amongst the ranks.

With the development of weapons with increased firepower, it became necessary to disperse the infantry over a wider expanse of terrain. This made the unit less susceptible to high explosive and rapid fire weapons. From World War I, it was recognized that infantry were most successfully employed when using their ability to maneuver in constricted terrain and evade detection in ways not possible for other weapons such as vehicles. This decentralization of command was made possible by improved communications equipment and greater focus on small unit training.


The most important role of the infantry has been as the primary force of an army. It is the infantry which ultimately decides whether ground was held or taken, and it is the presence of infantry that assures control of territory. While the tactics of employment in battle have changed, the basic missions of the infantry have not.

Attack operations are the most basic role of the infantry, and along with defense, form the two primary stances of the infantry on the battlefield. Traditionally, in an open battle, or meeting engagement, two armies would maneuver to contact, at which point they would form up their infantry and other units opposite each other. Then one or both would advance and attempt to defeat the enemy force. The goal of an attack remains the same: to advance into an enemy-held objective and dislodge the enemy, thereby establishing control of the objective. Attacks are often feared by the infantry conducting them due to the high number of casualties suffered while advancing under enemy fire. Successful attacks rely on sufficient force, preparative reconnaissance and bombardment, and retention of unit cohesion throughout the attack.

Defense operations are the natural counter to attacks, in which the mission is to hold an objective and defeat enemy forces attempting to dislodge the defender. Defensive posture offers many advantages to the infantry, including the ability to use terrain and constructed fortifications to advantage and the reduced exposure to enemy fire compared with advancing forces. Effective defense relies on minimizing losses to enemy fire, breaking the enemy's cohesion before their advance is completed, and preventing enemy penetration of defensive positions.

Patrol is the most common infantry mission. Full scale attacks and defensive efforts are occasional, but patrols are constant. Patrols consist of small groups of infantry moving about in areas of possible enemy activity to discern enemy deployments and ambush enemy patrols. Patrols are used not only on the front-lines, but in rear areas where enemy infiltration or insurgencies are possible.

Pursuit is a role that the infantry often assumes. The objective of pursuit operations is the destruction of enemy forces which are not capable of effectively engaging friendly units before they can build their strength to the point where they are effective. Infantry traditionally have been the main force to overrun these units in the past, and in modern combat are used to pursue enemy forces in constricted terrain (urban areas in particular), where faster forces, such as armored vehicles are incapable of going or would be exposed to ambush.

Escort consists of protecting other units from ambush, particularly from other infantry. This is one of the most important roles for the modern infantry, in particular when operating along side armored vehicles. In this capacity, infantry essentially conducts patrol on the move, scouring terrain which may hide enemy infantry waiting to ambush friendly vehicles, and identifying enemy strong points for attack by the heavier units.

Maneuver operations consume much of an infantry unit's time. Infantry, like all combat units, are often maneuvered to meet battlefield needs, and often must do so under enemy attack. The infantry must maintain their cohesion and readiness during the move to ensure their usefulness when they reach their objective. Traditionally, infantry have relied on their own legs for mobility, but modern infantry often uses trucks and armored vehicles for transport.

Reserve assignments for infantry units involve deployment behind the front, although patrol and security operations are usually maintained in case of enemy infiltration. This is usually the best time for infantry units to integrate replacements into units and to maintain equipment. Additionally, soldiers can be rested and general readiness should improve. However, the unit must be ready for employment at any point.

Construction can be undertaken either in reserve or on the front, but consists of using infantry troops as labor for construction of field positions, roads, bridges, airfields, and all other manner of structures. The infantry is often given this assignment due to the quantity of men within the unit, although it can lessen a unit's morale and limit the unit's ability to maintain readiness and perform other missions.


The equipment of infantry forces has evolved along with the development of military technology in general, but certain constants remain regarding the design and selection of this equipment. Primary types of equipment are weaponry, protective gear, survival gear, and special equipment.

Infantry weapons include all types of personal weapons, i.e. anything that can be handled by individual troops, as well as some small crew-served weapons that can be carried and used by infantry. Modern infantry weaponry include rifles, machine guns, shoulder-fired rocket launchers and missiles, and lighter mortars and grenade launchers. Older examples of infantry weapons include all sorts of melee weapons and some light ranged weapons such as spears, bows, and slings. During operations, especially in modern times, infantry have a tendency to scavenge and employ whatever weapons they can acquire in addition to those given them by their superiors.

Infantry protective gear includes all equipment designed to protect the soldier against enemy attack. Most protective gear comprises body armor of some type. Classical and Medieval infantry employed leather and metal armor as defense against both ranged and melee attacks, but with the advent of firearms, such armor could no longer defeat attacks and was discarded. The return to use of the helmet was prompted by the need to defend against high explosive fragmentation, and further developments in materials led to effective bullet-defeating armor within the weight acceptable for infantry use. The use of body armor is again becoming widespread amongst infantry units, primarily using Kevlar technology. Infantry must also often carry protective measures against chemical and biological attack, including gas masks, counter-agents, and protective suits.

Infantry survival gear includes all of the items soldiers require for day-to-day survival in the combat environment. These include basic environmental protections, medical supplies, food, and sundries. Traditionally, infantry have suffered large casualty rates from disease, exposure, and privation--often in excess of those suffered from enemy attacks. Better equipment of troops in this area greatly reduce this rate of loss. One of the most valuable pieces of gear is the entrenching tool--basically a small shovel--which can be employed not only to dig important defenses, but also in a variety of other daily tasks and even as an effective weapon.

Specialized equipment consists of a variety of gear which may or may not be carried depending on the mission and the level of equipment of an army. Communications gear has become a necessity, as it allows effective command of infantry units over greater distances. In some units, individual communications are being used to allow the greatest level of flexibility. Engineering equipment, including demolitions, mines, and other gear, is also commonly carried by the infantry or attached specialists. A variety of other gear, often relating to a specific mission, or to the particular terrain in which the unit is employed, can be carried by infantry units.

There are some general rules to which all infantry equipment must adhere to be effective and widely adopted:

  • Reliability: Equipment failure is fatal to the infantry, and if equipped with unreliable gear, morale will suffer greatly. Soldiers tend to prefer reliable proven technology to new, unproven gadgets. Additionally, the conditions in which infantry operate are often extreme and gear must be able to survive and operate in these conditions without fail.
  • Utility: Infantry have very limited weight capacity, and thus gear which does not help them do their job will be discarded.
  • Availability: Since infantry units are often large, and must be able to be raised in quantity, a particular tool must be available in sufficient quantity to equip the units. This means that it must be inexpensive enough to afford in quantity during peacetime, and producible enough to meet wartime demands.
  • Simplicity: Infantry relies on large numbers of troops, often conscripted and therefore of lesser quality than those available to other branches. An army must be able to train its troops uniformly in minimal time on the tools of the trade. Overly complex gear will often be useless in combat due to a lack of training or the difficulty of maintenance under field conditions.

Historical descriptions

  • "I love the infantry because they are the underdogs. They are the mud-rain-frost-and-wind boys. They have no comforts, and they even learn to live without the necessities. And in the end they are the guys that wars can't be won without." Ernie Pyle
  • "I'm convinced that the infantry is the group in the army which gives more and gets less than anybody else." Bill Mauldin, Up Front (1945)
  • "Queen of Battle." — motto of the United States Army Infantry, in reference to the queen chess piece.
  • "Follow me" — motto of the United States Army Infantry School
  • "To seek out and close with the enemy; to kill or capture him; to seize and hold ground; to repel attack, by day or night, regardless of season, weather or terrain" — The stated role of the Royal Australian Infantry Corps, an Arms Corps of the Australian Army.
  • "The infantry doesn't change. We're the only arm of the military where the weapon is the man himself." C.T. Shortis
  • "Ah, yes, mere infantry — poor beggars…" Plautus
  • "To close with and engage the enemy in all operational environments, in order to bring about his defeat" The British Army Infantry Mission
  • "The Infantry to be structured, equipped, manned, trained and motivated to fulfil its Mission, in accordance with the British Army's Manoeuvrist doctrine. It must be capable of successful, high tempo and sustained Warfighting, in concert with other Arms, as part of a light, medium or heavy force in a Joint or Multinational context. The Infantry must be able to operate simultaneously, across the spectrum of conflict prevention, conflict and post conflict activities, in all terrain, and in all environmental and climatic conditions." Director Of Infantry's Intent, DInf, British Army


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