Heavy infantry consisted of heavilyarmed andarmouredinfantrymen who were trained to mountfrontal assaults and/or anchor the defensive center of abattle line. This differentiated them fromlight infantry who were relativelymobile and lightly armouredskirmisher troops intended forscreening,scouting, and other tactical roles unsuited to soldiers carrying heavier loads. Heavy infantry typically made use ofdense battlefield formations, such asshield wall orphalanx,multiplying their effective weight of arms withforce concentration.

Heavy infantry were critical to many ancient armies, such as the Greekhoplites, Macedonianphalangites, and Romanlegionaries. After the fall of Rome, heavy infantry declined in Europe but returned to dominance in theLate Middle Ages withSwiss pikemen and GermanLandsknechts. With the rise offirearms duringearly modern warfare, dense formations became increasingly hazardous, and heavy armours were either ineffective or too cumbersome to be tactically useful. By the early 18th century, heavy infantry were replaced byline infantry armed withmuskets andbayonets and wore noarmour.

Inancient Greece, the hoplite was a common form of heavy infantry. All hoplites had a shield and spear, and perhaps a helmet as well. Wealthier hoplites were able to afford bronze breastplate orlinothorax armor, while poorer hoplites wore little to no armor. The hoplite armor and shield were designed to block arrows and blows from spear points and swords. Hoplites would act as both a city watch and as an army in the field. Hoplites were thought of as a force to be reckoned with because they would form a phalanx—a tight band of spearmen—which aided them against lighter infantry and cavalry.

Herodotus described an elite infantry unit of 10,000 soldiers, which he called theImmortals, in the army of theAchaemenid Empire. They were heavily-armed, carrying wicker shields, short spears,quivers, swords or large daggers, andbow and arrow.^[1] Underneath their robes they worescale armour coats, which means they were not "heavily-armored" (even by ancient standards), but on the other hand, this would allow them to carry more weapons. The regiment was followed by a caravan of covered carriages, camels, and mules that transported rations separate than that of the rest of the army.^[1]

Alexander's army employed infantry known as the phalangite – soldiers equipped with a small shield and long pike and employed in a formation known as thesarissa phalanx. Alexander also had a flexible heavy infantry force known as theArgyraspides, or silver shields, who acted as his elite infantry. Post-Alexander Hellenistic states such asMacedonia,Seleucid Persia, andPtolemaic Egypt would employ more heavily armored phalangites, as well as their own variation of elite units such as the silver shields.

TheCelts were a diverse group of people that, through migration, lived in an area stretching from theBritish Isles toAnatolia. A people with a strong warrior tradition, they varied greatly in battle and equipment. Some of the more heavily armed Celts woremail armour and "Galea" type helmets, and threwjavelins in battle; all of these elements were later adopted by the Romans. Celts were respected for their battle prowess and often served as mercenaries for other Mediterranean civilizations.^[2]

In themilitary of ancient Rome, heavy infantry made up most of the Roman army. The heavy infantry of thepre-MarianRoman Republic included thehastati,principes, andtriarii (although depending how thehastati were armed and armored, they could also be considered light infantry). Thehastati, the youngest men in the line, were armed with a sword, orgladius, and two javelins, orpila. Thepila were usually thrown at a charging enemy before they were engaged in hand-to-hand combat.Hastati were also equipped with a helmet, a shield and a bronze breast plate or coat of mail (if they could afford it). Theprincipes were armed just like thehastati, but they were older, more experienced and, because they had more money, were more likely to own better-quality arms. The final type of heavy infantry were thetriarii. They were armed and armored just like theprincipes except that instead of wielding a sword or gladius, they used a large spear known as thehasta. Incidentally, thehastati were originally armed with this weapon, which gave them their name, but thehasta were eventually abandoned as Rome switched from a Greek-style hoplite phalanx to the manipular system. Thetriarii were the last vestige of this older style of warfare in the Roman republic. Thetriarii were usually called in to end the battle and break the lines of the enemy.

Rome's use of heavy infantry and a general lack of major cavalry forces meant they were stronger in pitched battle but more vulnerable to ambushes. After the late 2nd century BCE, the three-lined maniples were replaced in favor of a single type of heavy infantry, the legionary, all equipped in nearly identical fashion tohastati andprincipes.

Following the introduction of infantry tactics during theWarring States period, theQin army developed an infantry force that would help it conquer the other states. Soldiers fulfilling the role of heavy infantry usually wore lacquered leather (and sometimes bronze) coat ofplate orlamellar armour, and were equipped with spears and wooden shields,halberds,dagger-axes, swords, and small and large shields covered in metal. Some soldiers were also equipped with very long spears, long halberds, or pikes, and fought in a formation akin to Swiss pikemen. TheHan dynasty that succeeded the Qin era equipped their soldiers with iron armor, which they were able to mass-produce because of state standardized metallurgical improvements. Unlike their contemporaries such as the post-Marian Romans, the Han military did not rely primarily on their heavy infantry but emphasized a more balanced force of infantry, missile troops, and cavalry.

The kingdom ofGoguryeo in Korea was renowned for its military power and influence, especially during the rule ofGwanggaeto the Great. The rapid expansion of Goguryeo intoManchuria and parts of eastern China can be accredited to the skill and discipline of the Goguryeo heavy infantry and cavalry. Soldiers were typically equipped with iron swords,polearms, and bows. Warriors were usually clad in iron lamellar armor or lacquered leather to ward off arrows and sword blows. The weapons and armor of the heavy infantry of Goguryeo were considered the best in quality because of the advanced technological improvements made in steel and iron production in Korea. Not much is known about the actual battle formations used in Korean armies during the Goguryeo era, but accounts of the individual expertise and prowess of the Goguryeo soldiers, as well as the strict regimentation of Goguryeo's armies, indicates that there must have been some balance between group combat and individual combat. Despite strides made in infantry warfare, Goguryeo also placed great emphasis on the usage of heavy cavalry, sometimes almost exclusively using horsemen for shock attacks, with infantrymen coming in after the initial cavalry charge. Meticulous development and implementation of efficient swordsmanship and martial arts, tactics, and technology allowed Goguryeo armies to remain virtually undefeated during the height of its existence.

The Swiss reinvented heavy infantry during the Late Middle Ages to counterheavy cavalry. Swiss pikeman militia formations resembled ancient Greek warfare and hoplite forces. Despite similarities with Greek phalanx formation, the Swiss showed more offensive posture during battles. The Swiss soldiers wore only steel caps and breastplates for protection. They were armed with halberds, which allowed footmen to pull cavalry soldiers from their mounts. The Swiss used drums to control formations. One additional factor that lessened heavy cavalry's role on the battlefield, despite innovations such as thestirrup, were the inventions of thelongbow and thecrossbow after the eleventh century. However, the Swiss did not manage to form an effective counter to heavy cavalry until the mid-fourteenth century. By the late fourteenth century the Swiss tactics started to dominate warfare. German, French and Spanish militaries incorporated Swiss mercenaries and adopted their heavy infantry tactics. The Swiss innovations continued to influence earlyRenaissance period.^[3]

• Light infantry
• Mechanized infantry in modern times
• Heavy cavalry
• Light cavalry
• Roman infantry tactics, strategy and battle formations