Ukraine

I think the main factor to the collapse as well as to why it was taking this long was the speed of communication. Those vassals had the luxury of 10 messages a year from the boss.

Interestingly, when it comes to (hopefully soon) collapse of russia, there are two parts to it. First are the instant communication channels that are useful to the crash and second is the human hierarchy that pootin uses (and has to) to get information. So he's at the Ottoman speeds of processing information, but at the modern speed of attack.