For a thousand years the walls of Constantinople had turned back every army that came against them. The city was the last living fragment of the Roman Empire — diminished and encircled, but unbroken.
In the spring of 1453 the Ottoman sultan Mehmed II brought cannon of a size the world had not seen, and after fifty-three days of siege the walls gave way. The city fell on the 29th of May; its last emperor died in the breach.
Historians have long used the date to close the medieval age. Scholars fleeing west carried Greek manuscripts into Italy, feeding the Renaissance; the blocked land routes east pushed Europe toward the oceans. One ending seeded several beginnings.