Screwing With World History for Fun and... Well, Only Fun:

[Ludens]

It was basically some bunch of soldiers (around 600 men IIRC) that was close to Constantinople when most of the garnision and the ruler (Baldwin II) rode out in a campaign to fight the Bulgars (IIRC). They knew that Baldwin II wasn't exactly popular so because of some reason they decided to sneak into the city. They succeeded and it triggered a rebellion that kicked out the former garnision.
When Baldwin II came back after his campaign he found the city in enemy hands and had lost his kingdom.

Intesting. Thanks for sharing .

[littlebktruck]

The Byzantine Empire split into 3 successor states after the loss of Constantinople. One of these, the Empire of Nicaea, would retake Constantinople in 1261.