To carry out his plan, Brauchitsch set up two army groups Army Group South, consisting of the Eighth, Tenth and Fourteenth armies, and Army Group North, made up of the Third and Fourth armies. The southern army group, under the command of General von Rundstedt, was to attack from Silesia in the general direction of Warsaw, scatter opposing Polish forces and occupy as early as possible with forces as strong as possible the Vistula on both sides of Warsaw with the aim of destroying the Polish forces still holding out in western Poland in co-operation with Army Group North. The first mission of the latter group was to establish connection between the Reich and East Prussia by driving across the Corridor. Detailed objectives of the various armies were outlined as well as those for the Air Force and Navy. Danzig, said Brauchitsch, would be declared German territory on the first day of hostilities and would be secured by local forces under German command.
A supplemental directive issued at the same time stipulated that the order of deployment for White would be put into operation on August 20. All preparations, it laid down, must be concluded by that date.
William L. Shirer, The Rise and Fall of the Third Reich
Case White update at #5.