People put too much emphasis on geography as the deciding factor if a nation survives, prospers or gets conquered. Yes it is a factor, but the more important one is the internal structure of the nation in question.Eh, as pointed by posters of the past, geography and such screw Poland as well. Russia is CLOSE. As Germany.
If geography was as important as people say it is, China would have long been conquered by someone else say like Tibet (good defensive terrain). northern Germany is not that much different than Poland geographically, its potentially flatter also and this is the area where Brandenburg the later unifier of German lands was located.