Phalanx vs Legion: which ancient formation was better?

Quick answer

Why did the Roman legion beat the phalanx?

The legion beat the phalanx through flexibility and terrain. The phalanx was almost unstoppable head-on but vulnerable on the flanks and on rough ground. At Cynoscephalae in 197 BC a Roman detachment struck it in the rear, and at Pydna in 168 BC it lost its cohesion on broken ground as the legion's smaller units pushed into the gaps.

For centuries two infantry systems defined ancient warfare in the Mediterranean, and when they finally met, one broke the other. The Macedonian phalanx was a moving wall of pikes; the Roman legion was a grid of sword-armed blocks that could bend without breaking. Their contest helped decide who would rule the Mediterranean world.

	The Phalanx	The Legion
Era	Greek and Macedonian, roughly 7th to 2nd century BC	Roman, from about the 4th century BC
Formation	A dense block bristling with long pikes	Flexible lines of maniples, later cohorts
Main weapon	The long pike (sarissa) and shield wall	The javelin (pilum) and short sword (gladius)
Strength	Nearly unstoppable head-on, on flat open ground	Adaptable to rough ground and to the flanks
Weakness	Vulnerable on the flanks and on broken terrain	Less raw shock power in a straight frontal push
Verdict	Beaten by the legion at Cynoscephalae and Pydna	Its flexibility won out and outlasted the phalanx

Key points

The phalanx was almost unstoppable head-on: a hedge of long pikes, called sarissas, that no frontal charge could reach.
Its weakness was the flank and rough ground, where the tight formation lost its cohesion.¹
The Roman legion fought in smaller, flexible units that could turn, reinforce and exploit gaps.
Rome beat Macedon at Cynoscephalae in 197 BC and Pydna in 168 BC, ending the age of the phalanx.²

The phalanx: a hedge of pikes

The Macedonian phalanx packed men shoulder to shoulder behind pikes up to about six meters long, held so that four or five rows of points projected ahead of the front rank. On open, level ground it was overwhelming, and it carried Alexander the Great across Persia. But the same density that made it deadly from the front made it clumsy: it could barely turn, and once its neat line was broken by hills, gullies or gaps, individual pikemen were nearly helpless in a close fight.³

Line drawing of a block of pikemen in perspective, the long pikes of the front ranks leveled forward — A syntagma, the basic block of the Macedonian phalanx: 256 men in a 16 by 16 square, the front ranks leveling their sarissas. Drawing from Theodore Ayrault Dodge's Alexander, 1890. Public domain

The legion: flexibility in the ranks

The Roman legion answered with organization. It was built from maniples, and later cohorts, that fought with the short sword and the heavy javelin, the pilum. Because the legion moved in many small blocks rather than one long line, it could face a threat from any direction, feed fresh men into the fight, and pour into any opening in the enemy formation. Where the phalanx was a single brittle wall, the legion was many walls that could each act on their own.⁴

Long stone relief on Trajan's Column crowded with Roman legionaries fighting Dacian warriors among trees, AD 113 — Roman legionaries in battle against the Dacians on Trajan's Column (AD 113), plate XXXII of Conrad Cichorius's 1896 publication of the reliefs. These are soldiers of the later imperial legion. Public domain

A wall that cannot turn will always lose to a line that can.

The verdict: why Rome won

When the two systems met, terrain and flexibility decided it. At Cynoscephalae in 197 BC the Macedonian right was winning until an unnamed Roman tribune led some twenty maniples into its rear; at Pydna in 168 BC the phalanx lost its cohesion on broken ground and Roman units pushed into the gaps and cut it down. The legion did not out-muscle the phalanx; it out-adapted it. Learn how each system worked in what was a phalanx and how the Roman legion worked, or see them in action among the greatest battles of antiquity.⁵

Line drawings of relief panels showing Roman and Macedonian soldiers and horsemen in combat — The frieze of the monument of Lucius Aemilius Paullus at Delphi, which celebrated his victory over Perseus of Macedon at Pydna in 168 BC; line drawing published by Salomon Reinach, 1909. Public domain

Frequently asked questions

What is the difference between a phalanx and a legion?

A phalanx is a single dense block of infantry fighting with very long pikes, powerful from the front but rigid. A Roman legion fought in many smaller, flexible units armed with sword and javelin, able to maneuver and adapt.

Was the Macedonian phalanx unbeatable?

Only from the front and only on level ground. Head-on, its hedge of pikes was almost impossible to break, but on rough terrain or against its flanks the formation came apart.

Why did the Roman legion beat the phalanx?

Flexibility and terrain. At Cynoscephalae in 197 BC a Roman detachment struck the phalanx in the rear; at Pydna in 168 BC it lost its cohesion on broken ground, and the legion's smaller units pushed into the gaps.⁶

Did the Romans ever use a phalanx?

Early Rome fought in a phalanx-style formation, but replaced it with the more flexible manipular legion, better suited to varied enemies and terrain.⁷

Sources

World History Encyclopedia (Joshua J. Mark), “The Greek Phalanx”

Livius.org (Jona Lendering), “Cynoscephalae (197 BCE)”

Imperium Romanum (imperiumromanum.pl), “Bitwa pod Kynoskefalaj” (in Polish)

Adrian Goldsworthy, The Complete Roman Army (Thames & Hudson, 2003).

Imperium Romanum (imperiumromanum.pl), “Bitwa pod Pydną” (in Polish)

Polybius, Histories, Book 18, 24 to 26 (Cynoscephalae: an unnamed tribune with about twenty maniples falls on the rear of the victorious Macedonian right) and 28 to 32 (phalanx compared with legion: the sarissa, five pike-points projecting before each front-rank man at 18.29, the need for level, unbroken ground at 18.31). Loeb translation online at LacusCurtius: https://penelope.uchicago.edu/Thayer/E/Roman/Texts/Polybius/18*.html.

Lawrence Keppie, The Making of the Roman Army: From Republic to Empire (Batsford, 1984).

Plutarch, Life of Aemilius Paullus, Chapter 20 (Pydna: on uneven ground the phalanx could not keep its shields locked; Aemilius sends his units into the gaps). Loeb translation online at LacusCurtius: https://penelope.uchicago.edu/Thayer/E/Roman/Texts/Plutarch/Lives/Aemilius*.html.