Divide and rule

Divide and rule (), or divide and conquer, 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 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. Niccolò Machiavelli identifies a similar application to military strategy, advising in Book VI of "The Art of War" (1521) ("L'arte della guerra"): a Captain should endeavor with every art to divide the forces of the enemy. Machiavelli advises that this act should be achieved 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. It was utilised by the Roman ruler Julius Caesar and the French emperor Napoleon (together with the maxim "divide ut regnes)".
The strategy, but not the phrase, applies in many ancient cases: the example of Aulus Gabinius exists, parting the Jewish nation into five conventions, reported by Flavius Josephus in Book I, 169–170 of "The Jewish War" ("De bello Judaico"). Strabo also reports in "Geographica", 8.7.3 that the Achaean League was gradually dissolved under the Roman possession of the whole of Macedonia, owing to their 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 of France to the House of Habsburg. Edward Coke denounces it in Chapter I of the Fourth Part of the "Institutes of the Lawes of England", 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 invincible 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.] 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 Sketch"
by 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" (If you commit a crime, deny it).
Elements of this technique involve:
Historically, this strategy was used in many different ways by empires seeking to expand their territories.
Immanuel Kant was an advocate of this tactic, noting that "the problem of setting up a state can be solved even by a nation of devils" so long as they possess an appropriate constitution which pits opposing factions against each other with a system of checks and balances.
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.
Foreign policy.
Divide and rule can be used by states to weaken enemy military alliances. This usually happens when propaganda is disseminated within the enemy states in an attempt to raise doubts about the alliance. Once the alliance weakens or dissolves, a vacuum will allow the state to achieve military dominance.
Politics.
In politics, 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 to prevent a rebellion against the elites or the people implementing the strategy. The goal is either to pit the lower classes against themselves to prevent a revolution, or to provide a desired solution to the growing discord that strengthens the power of the elites.
The principle "divide et impera" is cited as a common in politics by Traiano Boccalini in "La bilancia politica".
Narcissistic Parenting.
In families where one or both parents shows traits of Narcissistic Personality Disorder (NDP), they will attempt control of their children through a technique akin to political "divide et impera" by pitting child against child in a struggle for their affection. A common practice by the narcissistic parent is to designate a 'golden-child' who receives praise and can do no wrong, and a 'scape-goat' who gets the blame for everything that goes wrong, but this is used by the narcissist to further divide them by keeping both children in a state of insecurity about their positions in the family. In their battle to receive the limited supply of approval from the parent, they will see each other as a threat, and the parent can assume the role of saviour when they intervene to calm the aggression they created.
Psychopathy in the workplace.
Clive R. Boddy found that "divide and conquer" was a common strategy by corporate psychopaths used as a smokescreen to help consolidate and advance their grip on power in the corporate hierarchy.
Historical examples.
United States.
Harry G. Broadman opined in Forbes regarding President Donald Trump: "[a]s in his campaign, the President has been successfully—at least to date—pursuing a divide and conquer strategy domestically and internationally to try to achieve his goals. The result is an absence of a robust set of checks and balances to ensure that the best economic interests of the U.S. and the world will be served." 
Examples of this strategy are not entirely limited to deliberate efforts from U.S. Politicial Candidates. Political divide is a systemic problem with bipartisan politics itself, with numerous examples of divided interest among competing politicians adversely sowing divide among the populace they are meant to represent, across many countries. The effects of 'divide and rule' strategies are not always the result of a deliberate effort to control the population.