how can I achieve this ww2 map animation in After Effects?

I saw this map animation in this WW2 documentary on youtube. I'm trying to replicate this in After Effects and I'm currently stuck trying to figure the best way to do it. Should I use multiple layers? From what I can tell it seems like there's a whole layer beneath the same duplicated layer that then splits in two showing Germany before and after the Versailles Treaty. But I can't figure out the best way to do it in After Effects. Thank you in advance for any help or tips on how to achieve it.  

https://www.youtube.com/watch?v=mkavFs40yP8&t=817s