In 235 CE the death of Emperor Severus Alexander at the hands of his own soldiers began the ‘crisis’ of the third century during which numerous contenders fought for control of the empire. During this period of diminished imperial power, two breakaway states formed on the eastern and western fringes of the Roman Empire. In 260 CE the Gallic Empire split from Rome when soldiers in Gaul learnt of Emperor Valerian’s death and proclaimed their commander Postumus as emperor. Postumus ruled until 268 CE and expanded the Gallic Empire to control Britain and parts of Spain. The Palmyrene Kingdom began incursions into nearby territory after the death of King Odenaethus, who was subordinate to Rome, and in 271 CE its new ruler Queen Zenobia declared herself empress. Aurelian defeated Zenobia at the Battle of Immae in 272 CE and quickly extinguished the rebellion in Palymra before moving west to remove the Gallic Empire in 274 CE.
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