In 58 BC, Julius Caesar embarked on a campaign that transformed Gaul—modern France, Belgium, and beyond—into a Roman province . What propelled this conquest? Strategic fears had long haunted Rome, from the Gallic sack of the 390s BC to Germanic pressures across the Rhine. Economic prospects tantalized as well. Yet Caesar’s ambition loomed largest, and his victories reshaped what had been a frontier into the Roman Empire’s heartland.