Heavy infantry in the context of "Phalanx"

Infantry, or infantryman are a type of soldier who specialize in ground combat, typically fighting dismounted. Historically the term was used to describe foot soldiers, i.e. those who march and fight on foot. In modern usage, the term broadly encompasses a wide variety of subspecialties, including light infantry, irregular infantry, heavy infantry, mountain infantry, motorized infantry, mechanized infantry, airborne infantry, air assault infantry, and naval infantry. Other subtypes of infantry, such as line infantry and mounted infantry, were once commonplace but fell out of favor in the 19th century with the invention of more accurate and powerful weapons.

Light infantry refers to certain types of lightly equipped infantry throughout history. They have a more mobile or fluid function than other types of infantry, such as heavy infantry or line infantry. Historically, light infantry often fought as scouts, raiders, and skirmishers. These are loose formations that fight ahead of the main army to harass, delay, disrupt supply lines, engage the enemy's own skirmishing forces, and generally "soften up" an enemy before the main battle. Light infantrymen were also often responsible for screening the main body of a military formation.

Following World War II, the term "light infantry" has evolved to include rapid-deployment units (including commando and airborne units) that emphasize speed and mobility over armor and firepower. Some units or battalions that historically held a skirmishing role retain their designation "light infantry" for the sake of tradition.

The spatha was a type of straight and long sword, measuring between 0.5 and 1 metre (20 and 40 inches), with a handle length of between 18 and 20 centimetres (7 and 8 inches), in use in the territory of the Roman Empire during the 1st to 6th centuries AD. Later swords, from the 7th to 10th centuries, like the Viking swords, are recognizable derivatives and sometimes subsumed under the term spatha.

The Roman spatha was used in war and in gladiatorial fights. The spatha of literature appears in the Roman Empire in the 1st century AD as a weapon used by presumably Celtic auxiliaries and gradually became a standard heavy infantry weapon by the 3rd century AD, relegating the gladius to use as a light infantry weapon. The spatha apparently replaced the gladius in the front ranks, giving the infantry more reach when thrusting. While the infantry version had a long point, versions carried by the cavalry had a rounded tip that prevented accidental stabbing of the cavalryman's own foot or horse.

The Byzantine army was the primary military body of the Byzantine armed forces, serving alongside the Byzantine navy. A direct continuation of the Eastern Roman army, shaping and developing itself on the legacy of the late Hellenistic armies, it maintained a similar level of discipline, strategic prowess and organization. It was among the most effective armies of western Eurasia for much of the Middle Ages. Over time the cavalry arm became more prominent in the Byzantine army as the legion system disappeared in the early 7th century. Later reforms reflected some Germanic and Asian influences—rival forces frequently became sources of mercenary units, such as the Huns, Cumans, Alans and (following the Battle of Manzikert) Turks, meeting the Empire's demand for light cavalry mercenaries. Since much of the Byzantine military focused on the strategy and skill of generals utilizing militia troops, heavy infantry were recruited from Frankish and later Varangian mercenaries.

From the 6th to the 12th centuries, the Byzantine army was among the most powerful and effective military forces in the world – neither Middle Ages Europe nor (following its early successes) the fracturing Caliphate could match the strategies and the efficiency of the Byzantine army. Restricted to a largely defensive role in the 7th to mid-9th centuries, the Byzantines developed the theme system to counter the more powerful Caliphate. From the mid-9th century, however, they gradually went on the offensive, culminating in the great conquests of the 10th century under a series of soldier-emperors such as Nikephoros II Phokas, John Tzimiskes and Basil II. The army they led was less reliant on the militia of the themes; it was by now a largely professional force, with a strong and well-drilled infantry at its core and augmented by a revived heavy cavalry arm. With one of the most powerful economies in the world at the time, the Empire had the resources to put to the field a powerful host when needed, in order to reclaim its long-lost territories.

The Battle of Cannae (/ˈkæni, -eɪ, -aɪ/; Latin: [ˈkanːae̯]) was a key engagement of the Second Punic War between the Roman Republic and Carthage, fought on 2 August 216 BC near the ancient village of Cannae in Apulia, southeast Italy. The Carthaginians and their allies, led by Hannibal, surrounded and practically annihilated a larger Roman and Italian army under the consuls Lucius Aemilius Paullus and Gaius Terentius Varro. It is regarded as one of the greatest tactical feats in military history and one of the worst defeats in Roman history, and it cemented Hannibal's reputation as one of antiquity's greatest tacticians.

Having recovered from their losses at Trebia (218 BC) and Lake Trasimene (217 BC), the Romans decided to engage Hannibal at Cannae, with approximately 86,000 Roman and allied socii troops. They massed their heavy infantry in a deeper formation than usual, while Hannibal used the double envelopment tactic and surrounded his enemy, trapping the majority of the Roman army, who were then slaughtered. Later historians and military strategists have used Cannae as an exemplary battle of annihilation. The loss of life on the Roman side meant it was one of the most lethal single days of fighting in history; historian Adrian Goldsworthy equates the death toll at Cannae to "the massed slaughter of the British Army on the first day of the Somme offensive in 1916". Only about 15,000 Romans, most of whom were from the garrisons of the camps and had not taken part in the battle, survived. Following the defeat, Capua and several other Italian city-states defected from the Roman Republic to Carthage.

The Battle of Carrhae (Latin pronunciation: [ˈkar.rʰae̯]) was fought in 53 BC between the Roman Republic and the Parthian Empire near the ancient town of Carrhae (present-day Harran, Turkey). An invading force of seven legions of Roman heavy infantry under Marcus Licinius Crassus was lured into the desert and decisively defeated by a mixed cavalry army of heavy cataphracts and light horse archers led by the Parthian general Surena. On such flat terrain, the legion proved to have no viable tactics against the highly mobile Parthian horsemen, and the slow and vulnerable Roman formations were surrounded, exhausted by constant attacks, and eventually crushed. Crassus was killed along with most of his army. It is commonly seen as one of the earliest and most important battles between the Roman and Parthian Empires and one of the most crushing defeats in Roman history. According to the poet Ovid in Book 6 of his poem Fasti, the battle occurred on 9 June.

Crassus, a member of the First Triumvirate and the wealthiest man in Rome, had been enticed by the prospect of military glory and riches and decided to invade Parthia without the official consent of the Senate. Rejecting an offer from the Armenian King Artavasdes II to allow Crassus to invade Parthia via Armenia, Crassus marched his army directly through the deserts of Mesopotamia. His forces clashed with Surena's troops near Carrhae. Surena's cavalry killed or captured most of the Roman soldiers. Crassus himself was killed when truce negotiations turned violent, and his death ended the First Triumvirate.