divide and conquer

Short definition from Wiktionary

Verb

1. 1
   To use a combination of political, military and economic strategies that aim to gain and maintain power by breaking up larger concentrations of power into chunks that individually have less power than the one implementing the strategy.

Noun

1. 1
   A strategy for achieving political or military control.
2. 2
   An algorithm design technique that solves a problem by splitting it recursively into smaller problems until all of the remaining problems are trivial.
3. 3
   A phacoemulsification technique in which the nucleus is grooved and divided into halves.

Proverb

1. 1
   In order to rule securely, do not allow alliances between your enemies.