Read: 'The general's strategy proved prescient — the supply routes he had secured three months earlier became critical when the enemy cut off all other lines.' In context, 'prescient' most nearly means:

Context clues: the strategy was made '3 months earlier' and it 'proved' its value later — the general correctly anticipated a future need. 'Prescient' = having foreknowledge, foresighted, almost prophetically accurate. The prefix 'pre' (before) + Latin 'scire' (to know) = knowing beforehand. Context alone allows this deduction without knowing the root — the timing words 'three months earlier' and 'proved' signal that the strategy correctly anticipated future events.