divide

divide and rule (or conquer) the policy of maintaining supremacy over your opponents by encouraging dissent between them, thereby preventing them from uniting against you.

☞ This is a maxim associated with a number of rulers, and is found in Latin as divide et impera and in German as entzwei' und gebiete. Since the early 17th century, English writers have often wrongly attributed it to the Italian political philosopher Niccolò Machiavelli (1469–1527).