Studies of ancient warfare normally focus on the socio-political consequences of war, the moral character of commanders or the tactics employed in a single (usually dramatic) battle. Factors such as logistics, supply, strategy and scale are largely ignored. This paper will discuss a sorely underappreciated topic: the supply line of Caesar’s army during the Gallic War. It will investigate how the line was organised, when it was employed, and why the Romans ultimately abandoned it in favour of having supplies requisitioned from allies and conquered Gallic tribes. Caesar’s writing will be analysed in conjunction with archaeological evidence to explain how important this complex and underappreciated system of supply was, and how it successfully supported the Roman war-machine.