the.com/divide and conquer

means A strategy of splitting something large or unified — a problem, an opposing group, an army — into smaller parts so each part can be defeated or managed more easily than the whole.

from The political and military strategy is ancient, traced back to tactics described by Philip II of Macedon and later Roman rulers who kept conquered territories from uniting against them by fragmenting their alliances — the Latin phrase 'divide et impera' (divide and rule) captures it exactly. The 'conquer' version entered English as the maxim spread through European political writing, especially discussions of statecraft and empire, before computer scientists in the 20th century borrowed the phrase for algorithms that solve big problems by splitting them into smaller, more manageable subproblems — a peaceful echo of a very old, often ruthless, trick.