Estonia was first invaded by Soviets, then Nazis, then Soviets again, because even though Estonia didn't want to participate in either side, Soviets said not choosing a side means choosing enemy's side and they used this as an excuse to invade a fully-independent country.

Also, see https://en.wikipedia.org/wiki/Molotov–Ribbentrop_Pact for how Soviets and Nazis planned together the invasion of baltics and Eastern Europe.