From my admittedly limited understanding, Habsburg Austria maintained a multi-ethnic, multi-cultural, multi-linguistic, and multi-religious empire for several hundred years starting from 1526 - with the death of the childless Louis of Hungary and Bohemia, and the succession of those realms to his brother-in-law, Ferdinand I of Austria - until the end of WWI in 1918 and the events that followed afterwards. While long-lasting multi-ethnic empires aren't exactly a rarity in human history - and while the reasons for their longevity are well-known and documented - I feel that the Habsburg Austrian Empire is a unique subject in terms of these sorts of states: It existed in the middle of an era of rising liberalism and nationalism, it didn't have any particular protections or freedoms for ethnic minorities that I know of, and it was bordered alternately by two of the most powerful empires of the time and two of the most war-torn, strife-filled areas of the same era. Now, obviously, there must have been some traits that the Habsburg Austrian Empire possessed that made it capable of sustaining a multi-ethnic state through this tempestuous time period, but I'm exceedingly ignorant to whatever those might be. I was hoping that some more educated folks on here could enlighten me onto what this Empire had or did that made it so successful for so long. And, most importantly to the discipline of alternate history, what other states contemporary to 15th century Austria had or did those same things, and could have replaced the Habsburg Empire for those several hundred years? Thanks for any and all responses!