The siege of Constantinople in 1453 captivates our imagine, but there was another siege on the other side of the world that's largely forgotten, despite its equal significance. This was the siege of Xiangyang and Fan-ch’eng. Located near modern Hubei, these cities are on opposite sides of the Han River, which flows into the Yangtze. The two cities, supplied by the Song fleet on the river, stood astride the easiest way to invade China.
The siege lasted for five years, on and off, but the cities were ultimately taken when the Yuan built their own fleet to choke the cities off.
Suppose the city had held?