This is about all of the Slavic countries uniting in one large Slavic Union. As a pure slav myself I find that idea interesting... and sadly impossible thanks to conflict in between the Slavic brethren.
Uhhh no offense I really dislike these what if [insert historic event that will never happen / never would have happened / didn't happen] videos, I find them cheap. If you just watch them because you find the numbers in them interesting that's completely fine, but please refrain from posting them here in the future and for your sake don't live in the past or daydream about things that won't happen.
I find that these videos are very easy content to make and people make them because they know that it will get a lot of views, the comment sections are also always full of toxic, patriotic 14 and 50 year olds. Since this is not the first time something like this has been posted here I will just delete these kind of videos in the future. So no more "Russia vs USA war simulated" and "What if Russia joined the European Union and attacked China" videos etc. Thank you. (There won't be a 3rd world war in the foreseeable future, chill out)
This is a pretty good debate once again from Intelligence Squared.