Halley's Comet returned just as the Ottoman Empire under Sultan Mehmed II laid siege to the strategic fortress of Belgrade, Serbia, defended by Christian forces under John Hunyadi. The comet's tail resembled a golden saber, which filled both armies with superstitious terror. Pope Callixtus III ordered public prayers to avert the perceived wrath of the comet, which was widely feared to be an omen favoring the Ottoman advance, though the siege was ultimately repelled by Christian forces.

The terror of the saber-shaped comet spawned a wealth of Balkan epic poetry and Western anti-Ottman polemic verses. It cemented a long-lasting literary trope in Renaissance epic poetry where celestial weapons foretell massive, bloody clashes between competing global civilizations.