Roman Warfare & Expansion

Rome at War

Rome did not acquire its empire by accident. Over five centuries of nearly continuous warfare, the Roman army developed and adapted tactics, organisation and technology that allowed it to defeat opponents as varied as Macedonian phalanxes, Celtic warbands, desert guerrillas and Eastern cavalry. This lesson focuses on Roman warfare in the Imperial period and on two key conflicts: Trajan’s campaigns against the Dacians in the early second century AD, and the naval battle of Actium in 31 BC that determined who would rule the Roman world.

Tactics and Adaptability

The Roman army’s greatest strength was its capacity to adapt. When facing enemies who excelled in archery, Rome recruited auxiliary archers from Syria. When fighting desert nomads, it reorganised supply lines. The fundamental tactical approach, however, was consistent: use the pilum volley to disorder the enemy, close to sword range, and overwhelm with disciplined pressure from the scutum-wall.

Roman generals understood that battle was often decided before it started — by choosing ground, by tiring the enemy, by cutting off supply lines. The logistics of a Roman campaign were extraordinary: granaries at fortresses along the Rhine and Danube, a network of roads that allowed rapid troop movements, and a river fleet that carried supplies deep into enemy territory. Trajan’s Column records this infrastructure vividly — among its carved scenes are soldiers unloading supplies from boats and engineers constructing pontoon bridges.

Trajan’s Dacian Campaigns

Dacia, roughly equivalent to modern Romania, was a powerful kingdom north of the Danube ruled by a capable king named Decebalus. Decebalus had humiliated Rome in previous conflicts, extracting tribute money and capturing Roman prisoners. Trajan invaded in 101 AD to recover Roman prestige and to seize Dacian gold reserves that were among the largest in the ancient world. The first war ended with Decebalus surrendering and agreeing to Roman terms; when he broke those terms, Trajan launched a second, more brutal campaign that ended with the destruction of the Dacian capital Sarmizegetusa and Decebalus’s suicide rather than capture.

Trajan’s Column, standing in Rome, is a hollow marble column roughly 30 metres tall, around whose shaft winds a continuous carved relief depicting both campaigns in over 150 individual scenes. The column begins with river-gods and troops crossing a pontoon bridge and moves through sieges, battle scenes, negotiations and triumphal processions to the final conquest. The Arch of Trajan at Benevento, a triumphal arch decorated with relief panels, shows Trajan receiving submission from Dacian enemies, distributing grain to Roman citizens, and associating his victories with divine favour. Both monuments present the campaigns as evidence of Roman greatness and Trajan’s exceptional leadership.

Siege Warfare

Roman success against fortified towns and hillfort strongholds depended on specialised siege techniques. The standard approach involved surrounding the enemy position with a circumvallation — a wall or ditch that encircled the entire position and cut off all resupply. This was then supplemented by direct assault: battering rams mounted in wheeled towers, artillery firing stones and bolts, and approach ramps of earth built up to the level of the enemy walls. Trajan’s Column shows all of these techniques in use against Dacian hillforts.

The Battle of Actium, 31 BC

The naval battle of Actium was fought off the coast of north-western Greece on 2 September 31 BC. On one side was Octavian (the future Augustus) commanding a fleet under his brilliant admiral Marcus Agrippa. On the other were the combined forces of Mark Antony and Cleopatra VII of Egypt. The battle decided who would control the entire Roman world. Octavian’s victory made him undisputed master of Rome and led directly to the establishment of the Roman Empire.

The trireme had been the dominant warship of the classical Greek period, but by Actium the principal warships were larger vessels called quinqueremes and triremes built on a grander scale. Agrippa’s fleet used grappling hooks and boarding tactics to neutralise Antony’s heavier ships. When Cleopatra’s squadron broke off the engagement and retreated towards Egypt, Antony followed — and his remaining fleet, left without leadership, surrendered. The battle showed that naval supremacy could decide the fate of an entire empire.