Domen
Misico dux Vandalorum
were not undertaken solely as a blind for preparations for war
Hard to believe considering the scale of German preparations, also the main objectives of the Fall Weiss plan which were formulated already in the Spring of 1939.
Also one of features of negotiations is that you try to find the compromise between your and the other side's demands. In those "negotiations" Germany was gradually demanding more and more from Poland, instead of making concessions to find a solution satisfying for both sides.
Quoting from memory (since I'm currently at the University) - the shortest possible objective of the Fall Weiss was described as follows:
"The keynote of the invasion of Poland is to destroy the Polish Armed Forces. This will be achieved through concentric strikes - from Silesa towards Warsaw and from Pomerania and East Prussia towards Warsaw - in order to destroy the main Polish forces which are expected to resist in the area west of the Vistula-San and to cut off their withdrawal to the south-east".
This was the objective of the invasion plan established already in the Spring of 1939 - there was nothing about Free City Danzig in that plan.
If Germans wanted Danzig they would prepare for the annexation of Danzig, instead of for the destruction of Poland. Annexation of Danzig and the Polish "Corridor" was only one of many objectives of the German 4. Army, which was part of Army Group "North" and one of 5 armies designated to carry out the invasion.
Objectives of the 4. Army were to cut off and destroy the Polish Army "Pomerania", occupy Danzig, then capture bridgeheads over the Vistula as fast as possible and advance on Warsaw along both banks of the Vistula in cooperation with western wing of the 3. Army.
The "Fall Weiss" campaign was planned as a lightning war, in which special role was since the very beginning of the planning process reserved for motorized-armoured forces and Luftwaffe - and it was aimed at the destruction of the Polish army as fast as possible. It was not planned as merely an occupation of Free City Danzig but "accidentally turned out into the most stunning military conquest in history up to that point" - as Nazi apologists say.
and the complete conquest of all of Poland was not necessarily at stake
The only thing which could prevent Nazi invasion of Poland aimed at its destruction - was an alliance of Poland with Germany. Behaving like a submissive, but still not friendly at all, neighbour-state openly siding with France and Britain, but trying to prevent getting invaded - would not help Poland at all.
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Moreover, if Poland did not get under Nazi Germany's control - then where would Hitler find Jews to kill ???
Poland had the largest Jewish community of all European countries.