Woodcut from Historien vom Gallier und der Romer, published in Mainz in 1530 showing Julius Caesar sailing the Thames. In his Gallic Wars, Julius Caesar invaded Britain twice, in 55 and 54 BC. The second was more successful, setting up a friendly king, Mandubracius, and forcing the submission of his rival, Cassivellaunus, although no territory was conquered and held for Rome. Gaius Julius Caesar (100-44 BC) was a Roman general and statesman. He played a critical role in the gradual transformation of the Roman Republic into the Roman Empire. In military campaigns to secure Roman rule over the province of Gaul (present day France) he gained much prestige. The Roman senate, fearing his power, ordered him to disband his army, but Caesar refused, crossed the Rubicon River, returned to Rome with his army, and made himself dictator. On a subsequent campaign in Asia, he reported to the senate, "I came, I saw, I conquered." Caesar was assassinated by his friend Brutus and others on the Ides of March in 44 BC.