Invasion is not necessary. It is sad that any discussion limits politics and rivalry between countries to full-scale invasion.
Poland and Russia have opposing interests. Period. Russia wants to be a part of Europe, Poland doesn't want Russia to be a part of Europe. Poland wants to be sovereign country that keeps growing economically, Russia doesn't want that.
Russia doesn't need to invade Poland, it is enough to "reshape the European Security Architecture", reduce Polish chances to develop and growth etc.
Poland and Russia have opposing interests. Period. Russia wants to be a part of Europe, Poland doesn't want Russia to be a part of Europe. Poland wants to be sovereign country that keeps growing economically, Russia doesn't want that. Russia doesn't need to invade Poland, it is enough to "reshape the European Security Architecture", reduce Polish chances to develop and growth etc.