Divide and rule (or divide and conquer, from Latindīvide et imperā) in politics and sociology is gaining and maintaining power by breaking up larger concentrations of power into pieces that individually have less power than the one implementing the strategy. The concept refers to a strategy that breaks up existing power structures, and especially prevents smaller power groups from linking up, causing rivalries and fomenting discord among the people. It was heavily used by British Empire in India and elsewhere.
Traiano Boccalini cites "divide et impera" in La bilancia politica as a common principle in politics. The use of this technique is meant to empower the sovereign to control subjects, populations, or factions of different interests, who collectively might be able to oppose his rule. Machiavelli identifies a similar application to military strategy, advising in Book VI of The Art of War (Dell'arte della guerra), that a Captain should endeavor with every art to divide the forces of the enemy, either by making him suspicious of his men in whom he trusted, or by giving him cause that he has to separate his forces, and, because of this, become weaker.
The maxim divide et impera has been attributed to Philip II of Macedon, and together with the maxim divide ut regnes was utilised by the Roman ruler Caesar and the French emperor Napoleon.
The strategy, but not the phrase, applies in many ancient cases: the example of Gabinius exists, parting the Jewish nation into five conventions, reported by Flavius Josephus in Book I, 169-170 of The Wars of the Jews (De bello Judaico).Strabo also reports in Geography, 8.7.3 that the Achaean League was gradually dissolved under the Roman possession of the whole of Macedonia, owing to them not dealing with the several states in the same way, but wishing to preserve some and to destroy others.
The strategy of division and rule has been attributed to sovereigns, ranging from Louis XI to the Habsburgs. Edward Coke denounces it in Chapter I of the Fourth Part of the Institutes, reporting that when it was demanded by the Lords and Commons what might be a principal motive for them to have good success in Parliament, it was answered: "Eritis insuperabiles, si fueritis inseparabiles. Explosum est illud diverbium: Divide, & impera, cum radix & vertex imperii in obedientium consensu rata sunt." [You would be insuperable if you were inseparable. This proverb, Divide and rule, has been rejected, since the root and the summit of authority are confirmed by the consent of the subjects.] On the other hand, in a minor variation, Sir Francis Bacon wrote the phrase "separa et impera" in a letter to James I of 15 February 1615. James Madison made this recommendation in a letter to Thomas Jefferson of 24 October 1787, which summarized the thesis of The Federalist#10: "Divide et impera, the reprobated axiom of tyranny, is under certain (some) qualifications, the only policy, by which a republic can be administered on just principles." In Perpetual Peace: A Philosophical Sketchby Immanuel Kant (1795), Appendix one, Divide et impera is the third of three political maxims, the others being Fac et excusa (Act now, and make excuses later) and Si fecisti, nega (when you commit a crime, deny it).
Elements of this technique involve:
creating or encouraging divisions among the subjects to prevent alliances that could challenge the sovereign
aiding and promoting those who are willing to cooperate with the sovereign
fostering distrust and enmity between local rulers
encouraging meaningless expenditures that reduce the capability for political and military spending
Historically, this strategy was used in many different ways by empires seeking to expand their territories.
The concept is also mentioned as a strategy for market action in economics to get the most out of the players in a competitive market.
A primary strategy the narcissist uses to assert control, particularly within his/her family, is to create divisions among individuals. This weakens and isolates them, making it easier for the narcissist to manipulate and dominate. Some are favoured, others are scapegoated. Such dynamics can play out in a workplace setting.