The was was coming Justinian anyway, their claim on Danzig had little to do with it. The historical claim however is very dubious, as the city itself is hardly german at all (defenatly not german in the way the germans of that time considered it). It is true that it was part of German empire before that, and yes it belonged to Prussia, but it had a majority of slavic people and some of them were involved in the 19th century pan-slavic movement. So it can only be claimed as german as much as we Belgians could claim Lille (in France) as ours..
The USSR, at that time, was less of a threat, as it was only industrialising for 2 decades at that time. It had no economy to match the west, and it couldn't even fabricate weapons that were the equals of western weapons. The only thing that kept the russians going in WWII was massive aid from the west and pure terror.
Thus, claiming you'd rather have the Germans as a buffer against the Soviets, is utter bollocks, and even inhuman, as social groups were being eliminated on an industrious scale. Although that happened only during the war, the seeds and the plans were there since the 30's..
God: Behold ye angels, I have created the ass.. Throughout the ages to come men and women shall grab hold of these and shout my name...