200 ADSeptimius Severus-Septimius Severus came to power at the point of a sword. Severus first challenged Didius Julianus who was the highest bidder to become emperor at a auction held by the Praetorian Guard. Severus went on to defeat Septimius Albinus and Pescennius Niger, each head of his own legion and each claiming the right to be Emperor.
212 ADEdict Of Caracalla- Caracalla, the son of Septimus Severus who succeeded him after killing his brother, issued the Constitio Antoniniana. Although this edict extended Roman citizenship to all free inhabitants of the Empire, its value was limited since citizens actually had very few rights at this time.
220 AD Three Kingdoms- Six Dynasties- With the end of the Han Dynasty, Tsao Pei assumed power and founded the Wei Dynasty. The Wei dynasty was the first in a series of dynasties known as the Six Dynasties. While the Wei dynasty would eventually be recognized as the legitimate one, for some period of time, three competing kingdoms each claimed to be the legitimate rulers of China.
224 AD Battle Of Hormizdagan- Artabanus V, king of the Parthian Empire is defeated in the battle of Hormizdagan by Ardashir the shah of Persia. This proved the beginning of the Sassanid Empire.
235 AD The Roman Army On Rhine Revolts - Alexander Severus the Roman Emperor conducted an indecisive campaign against the Germanic tribes. Alexander Severus' troops revolted and killed him. Maximinus, a Thracian general, became the new emperor.
259 ADMarcus Postumus Defends Gaul-From 235 to 284 A.D., the Roman Empire was shaken by Civil War. There were 22 emperors and all but two met their deaths violently. During this period, both Germanic tribes in the north and Sassanid Persians in the east made inroads into the Empire.
274 ADBattle At Chalons - In 260 A.D., Marcus Postumus created a separate Gallic Empire. In 274 A.D. at the Battle of Chalons, his successor Pius Tetricus was defeated, thereby ending the short-lived Gallic Empire.
284 - 305 ADAge Of Diocletian - Diocletian became emperor in 284 A.D. He engaged in a series of reforms that reinvigorated the empire and transformed it. His actions launched the period that became known as the Late Empire.
Diocletian divided the empire into four administrative units each with its own rulers and administration. Diocletion strengthened the army as well as the civil service.
287 AD Aurelius Carausius Revolts-Aurelius Carausius, commander of the Roman fleet in the English Channel, revolted. He established England as an independent kingdom of Britain.
296 ADBritain Reinvaded By Romans- Constantius Chlorus invaded Britain. He defeated Allectus who had killed Marcus Aurelius Carausius. Britain was reintegrated into the Roman Empire and divided into four provinces.
296 AD Battle Of Carrhae - Artabanus V, King of the Parthian Empire, is defeated at the Battle of Hormizdagan by Ardashir, the Shah of Persia. This marked the beginning of the Sassanid Empire.