Here’s the summary for the wikipedia article you mentioned in your comment:

` Divide and rule policy (Latin: divide et impera), or divide and conquer, in politics and sociology is gaining and maintaining power divisively. Historically and presently, this strategy was and is used in many different ways by empires seeking to expand their territories; however, it has been hard to distinguish between the exploitation of pre-existing divisions by opponents, and the deliberate creation or strengthening of these divisions implied by “divide and rule”. 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 when it became part of the Roman province of Macedonia, as the Romans treated the various states differently, wishing to preserve some and to destroy others.Elements of this technique involve:

creating or encouraging divisions among the subjects to prevent alliances that could challenge the sovereign and distributing forces so that they overpower each other. 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 `

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