In 305 Constantine assisted his father, the newly appointed Western emperor, with a campaign in Britain. Their army proclaimed Constantine emperor after his father’s death the next year. A multisided civil war ensued between Constantine and the several other factions vying for the throne. Constantine defeated his main rival for the Western emperorship in 312 and defeated the Eastern emperor in 324 after years of strained relations, thus making Constantine sole ruler of the Roman Empire. He would direct largely successful campaigns for the rest of his reign, and he died in 337 while preparing for a campaign against the Persians.