What policy did the Romans pursue to increase the territory of their state?

The Romans developed military affairs to increase their state. A strong and professional army was created. New tactical methods of warfare were applied. The professionalism of the command was the basis for a successful battle. But besides the army, some tricks were also used. The rulers of Rome constantly pitted their enemies against each other. Enemies destroyed one one, and then, the Roman troops finished off the enemies, since they had a good army. The expression “Divide and Conquer” appeared. This is the principle of the foreign policy of ancient Rome.