Septimius Severus, in order to maintain the loyalty of the armies, raised the pay of legionaries, and gave substantial
donatives to the troops. This policy was maintained by his successors in the Severan dynasty. Over time the army required larger and larger bribes to remain loyal. The large and ongoing increase in military expenditure caused problems for all of his successors. Instead of warring in foreign lands, the Roman empire was increasingly put on the defensive by marauding enemies and civil wars. This cut off the essential source of income gained from plundering enemy countries, while opening up the Roman countryside to economic devastation from looters both foreign and domestic. Frequent civil wars contributed to depletion of the army's manpower, and drafting replacement soldiers strained the labour force further. Fighting on multiple fronts, increasing size and pay of the army, increasing cost of transport, populist "
bread and circuses" political campaigns, inefficient and corrupt tax collection, unorganised budgeting, and paying off foreign nations for peace all contributed to the financial crisis. The emperors responded by confiscating assets and supplies to combat the deficit. The situation of the Roman Empire became dire in 235. Many
Roman legions had been defeated during a previous campaign against
Germanic peoples raiding across the borders, while the emperor
Severus Alexander had been focused primarily on the dangers from the
Sasanian Empire. Leading his troops personally, the emperor resorted to diplomacy and accepting tribute to pacify the
Germanic chieftains quickly, rather than military conquest. According to
Herodian, this cost Severus Alexander the respect of his troops, who may have felt that more severe punishment was required for the tribes that had intruded on Rome's territory. The troops assassinated Severus Alexander and proclaimed the new emperor to be
Maximinus Thrax, commander of one of the legions present. Maximinus was the first of the
barracks emperors – rulers who were elevated by the troops without having any political experience, a supporting faction, distinguished ancestors, or a hereditary claim to the imperial throne. As their rule rested on military might and generalship, they operated as
warlords reliant on the army to maintain power. Maximinus continued the campaigns in
Germania but struggled to exert his authority over the whole empire. The Senate was displeased at having to accept a peasant as Emperor. This precipitated the chaotic
Year of the Six Emperors during which all of the original claimants were killed: in 238 a revolt broke out in Africa led by
Gordian I and
Gordian II, which was soon supported by the
Roman Senate, but this was quickly defeated with Gordian II killed and Gordian I committing suicide. The Senate, fearing the wrath of Maximinus, raised two of their own as co-Emperors,
Pupienus and
Balbinus, with Gordian I's grandson
Gordian III as
Caesar. Maximinus marched on Rome but was assassinated by his own troops, and subsequently Pupienus and Balbinus were murdered by the
Praetorian Guard. In the following years, numerous
Roman generals fought each other for control of the empire and neglected their duties of defending it from invasion. There were frequent raids across the
Rhine and Danube frontier by foreign tribes, including the
Carpians,
Goths,
Vandals, and
Alamanni, and attacks from the
Sasanian empire in the east.
Climate changes and a
sea level rise disrupted the agriculture of what is now the
Low Countries, forcing tribes residing in the region to migrate into Roman lands. Further disruption arose in 251, when the
Plague of Cyprian (possibly
smallpox) broke out. This plague caused large-scale death, severely weakening the empire. The situation was worsened in 260 when the emperor
Valerian was captured in battle by the Sasanians (he later died in captivity). Throughout the period, numerous
usurpers claimed the imperial throne. In the absence of a strong central authority, the empire broke into three competing states. The
Roman provinces of
Gaul,
Britain, and
Hispania broke off to form the
Gallic Empire in 260. The eastern provinces of
Syria,
Palestine, and
Aegyptus also became independent as the
Palmyrene Empire in 267. The remaining provinces, centered on Italy, stayed under a single ruler but now faced threats on every side. raids in the 3rd century An invasion of Macedonia and Greece by
Goths, who had been displaced from their lands on the
Black Sea, was defeated by emperor
Claudius II Gothicus at the
Battle of Naissus in 268 or 269. Historians see this victory as the turning point of the crisis. In its aftermath, a series of tough, energetic barracks emperors were able to reassert central authority. Further victories by Claudius Gothicus drove back the
Alamanni and recovered Hispania from the Gallic Empire. He died of the plague in 270 and was succeeded by
Aurelian, who had commanded the cavalry at Naissus. Aurelian reigned (270–275) through the worst of the crisis, gradually restoring the empire. He defeated the Vandals,
Goths, Palmyrene Empire, and finally the remainder of the Gallic Empire. By late 274, the Roman Empire had been reunited into a single entity. However, Aurelian was assassinated in 275, sparking a further series of competing emperors with short reigns. The situation did not stabilize until
Diocletian, himself a barracks emperor, reunified the empire in 285. More than a century would pass before Rome again lost military ascendancy over its external enemies. However, dozens of formerly thriving cities, especially in the Western Empire, had been ruined. Their populations dead or dispersed, these cities could not be rebuilt, due to the economic breakdown caused by constant warfare. The economy was also crippled by the breakdown in trading networks and the debasement of the currency. Major cities and towns, including Rome itself, had not needed fortifications for many centuries, but now surrounded themselves with thick
walls. Fundamental problems with the empire still remained. The right of imperial succession had never been clearly defined, which was a factor in the continuous civil wars as competing factions in the military, Senate, and other parties put forward their favored candidate for emperor. The sheer size of the empire, which had been an issue since the late
Roman Republic three centuries earlier, continued to make it difficult for a single ruler to effectively counter multiple threats at the same time. These continuing problems were addressed by the radical reforms of Diocletian, who broke the cycle of usurpation. He began by sharing his rule with a colleague, then formally established the
Tetrarchy of four co-emperors in 293. However the trend of civil war would continue after the abdication of Diocletian in the
Civil wars of the Tetrarchy (306–324) until the rise of
Constantine the Great as sole Emperor. The first
Roman emperor Augustus, who had established the ('Peace of Augustus') in the 1st century BC, had used the title ('leading citizen'). Historians call this first phase of Roman imperial rule the
Principate, as Augustus created a system of imperial government that maintained
Republican norms and consent given by the
Roman Senate. The
Principate period ended with the Crisis of the Third Century and the reign of Diocletian, who discontinued the use of the
princeps title; from his reign onward emperors used the title '' ('lords').'' The crisis resulted in such profound changes in the empire's institutions, society, economic life, and
religion that it is increasingly seen by most historians as defining the transition between the
historical periods of
classical antiquity and
late antiquity. The empire survived
until 476 in the West and
until 1453 in the East. == Causes ==