The Roman Empire was successful in expansion in part because it built upon the conquests and colonial strategies developed by the Roman Republic. The beginning of Roman expansion was its successes in the conquest mof Greece and the Punic wars during the Republic, which gave it control of the norther and western Mediterranean. Much of this success was due to a power vacuum, with the battles among the successor states to Alexander weakening them and leaving them open to conquest. The emperors Julius and August Caesar added Gaul and Britain and solidified control over Egypt. The Roman Empire's ability to hold its provinces was due to efficient administration.