It facilitated the start of the Qing dynasty before the Revolution, was invaded and held by the Japanese in 1931, then provided the final point of defence of the Nationalists at the end of the Civil War. Is this purely a coincidence? Or is there something I am missing about the significance of its location?
then provided the final point of defence of the Nationalists at the end of the Civil War
I'm not sure this part is really true. Some of the last areas controlled by the Nationalists on the Mainland were mostly in Sichuan and Yunnan in the Southwest, as well as Hainan Island.
Not sure I fully understand the question at all. Are you trying to say that somehow the rise of Qing is connected with being invaded by Japan 300 years later? Or are you trying to say that because 2 unconnected incidents happened in the area there is something significant about it? If it is the latter case, you can draw the same implications about every single historical region there is so I don't understand the confusion.