Constantinople fell due to one gate left open

As They Might Be Giants fans will attest, Istanbul was once known as Constantinople; nevertheless, it is currently known as Istanbul. However, the song does not provide an answer to the question of how Constantinople fell; rather, it is necessary to look at the history of the area, in particular, one crucial error made by those in charge of defending Constantinople during the siege that ultimately resulted in the Byzantine capital being captured by Ottoman forces.

The siege began on April 6, 1453, and lasted for 53 days. Since Constantine dedicated it, Constantinople had served as the imperial capital, and although being the target of numerous sieges, it had only been conquered once before—during the Fourth Crusade. Emperor Constantine XI Palaiologos had reason to be confident despite being greatly outnumbered by Sultan Mehmed II's armies because the city's walls had recently been repaired, the defenders were reasonably well-equipped, and it was widely believed that the Byzantine Empire could withstand the siege until assistance from the West arrived.

Despite being outnumbered, the Byzantine army held its own against Ottoman army skirmishes until just after midnight on May 29. The Genoese general in charge of the ground soldiers, Giovanni Giustianini, was severely hurt and had to be removed from the front lines during a significant fight that matched several Ottoman groups against various Byzantine strongholds.

Turkish troops were able to partially breach Constantinople's defences while rushing to get the general back into the safety of the city, raising Turkish flags in the process. Someone then neglected to lock one small, postern gate that went into the city as a result of a hurried retreat to try to defend the city's interior.

Large numbers of Ottoman soldiers were able to enter the city through that one gate, and from that point on, Constantinople was doomed to collapse. There are simply too many other circumstances, thus historians cannot conclusively state that Constantinople would have continued to be a part of the Byzantine empire in the absence of the error. But because the gate was left unlocked, a tiny breach developed into a successful assault, which ultimately led to Constantinople becoming Istanbul.

• Year: 1453