No one invaded it you fool.They are all local people from eastern ukraine.Russians helped them, thats true, but 90% of those pro-russian army are ukrainians.
Again, those guys did not come to that land, they have been there for centuries.Their family roots are from Donetsk and Luhansk region.
Solution is simple, let people decide in what country they want to live, and stop killing them cause they dont want NATO puppet for government.
Don't want to be a "NATO puppet" ? Pack your shit, sell your property and move across the border to your friendly "ethnic russian" friends. No one is holding you back.