Not a war, precisely...
... but a campaign: Alexander's conquest of Western Asia. It carried Classical Greek culture and knowledge with it (in which Alexander was tutored by no less than Aristotle himself), to be preserved and added to during Europe's "Dark Ages" by the eventual successors to power in those lands, the Arabs.
Europe's reawakening, of which we are the inheritors, was fueled by manuscripts brought back from "the Holy Land" (and adjacent territories).