In modern scholarship, the "late" period of the Roman army begins with the accession of the Emperor Diocletian in AD 284, and ends in 480 with the death of Julius Nepos, being roughly coterminous with the Dominate. During the period 395–476, the army of the Roman Empire's western half progressively disintegrated, while its counterpart in the East, known as the East Roman army remained largely intact in size and structure until the reign of Justinian I.
The Tetrarchs, a porphyry statue on Venice's Basilica di San Marco, shows the emperor Diocletian and his three imperial colleagues. To the left, Diocletian and Maximianus, the two Augusti (co-emperors); to the right, Galerius and Constantius Chlorus, the two Caesars (deputy emperors). Note the woollen "Pannonian" caps commonly worn (out of combat) by officers in the late army as a result of the pervasive influence of the Danubian officer class; and the sword grips with eagle-head pommels.
Reenactor wearing the typical equipment of a late 3rd-century foot soldier. The helmet is a Niederbieber type, with cross-pattern reinforcing ridges on the top of the bowl, and cheek-guards which can be fastened together. The sword is a spatha (median blade length 900 mm/36 inches), used by the cavalry only in the 1st and 2nd centuries. This soldier carries a spiculum, a heavy pilum-type javelin. Note the chain mail (lorica hamata) shirt and oval shield. Clothing consisted of a long-sleeved tunic, trousers and boots. The equipment of a 4th-century infantryman was very similar to the 3rd century, save that the
Fresco from the synagogue in the Roman fortified frontier city of Dura Europos dating to c. 250 AD. The centre shows unarmoured light cavalry charging with lances, the foreground and background show infantry fighting with spathae (long-bladed swords); they are equipped with knee-length scale armours, some with full-length sleeves.
Roman emperor Valerian (left, kneeling) begs for his life after being captured by Persian Shah Shapur I (mounted) at the Battle of Edessa (260), the most humiliating of the military disasters suffered by the empire in the late 3rd century. Rock relief at Naqsh-e Rostam near Shiraz, Iran
The Roman army was the armed forces deployed by the Romans throughout the duration of Ancient Rome, from the Roman Kingdom to the Roman Republic and the Roman Empire, and its medieval continuation, the Eastern Roman Empire. It is thus a term that may span approximately 2,206 years, during which the Roman armed forces underwent numerous permutations in size, composition, organisation, equipment and tactics, while conserving a core of lasting traditions.
Levy of the army, detail of the carved relief on the Altar of Domitius Ahenobarbus, 122–115 BC.
Gaius Marius, to whom later historians would misattribute putative reforms of the Roman army
Roman auxiliary infantry crossing a river. They can be distinguished by the oval shield (clipeus) they were equipped with, in contrast to the rectangular scutum carried by legionaries. Panel from Trajan's Column, Rome
Roman relief fragment depicting the Praetorian Guard, c. 50 AD
