The Central Powers overran Poland in 1915. Since then Germany and Austria-Hungary have been arguing about what to do with the conquered territory. The Germans favour the creation of an independent Poland (more like a semi-independent Poland, guided by Germany), while the Habsburgs think that Poland should be added to their empire. The Austro-Hungarians fear that the creation of a Polish state will cause unrest among their own Polish citizens in Galicia.
The Germans had initially agreed that Poland would go to the Austria-Hungary, despite the fact that it was primarily German arms that had conquered it. Since then though the failures of Austro-Hungarian arms have changed the dynamic of the relationship. Austria-Hungary is increasingly looking like little more than a German client state, with its army being taken over by German officers.
So now the Germans are able to revoke their previous agreement to hand Poland to Austria-Hungary. By joint agreement, the Central Powers today declare their intention to establish a Polish state after the war’s end.
The Germans hope that their declaration will make it easy for them to raise a Polish army to fight against the Russians. As part of their wooing of the Poles, they now halt the recruitment of forced labour battalions in Poland. Perhaps the Poles will be more inclined to join a pro-German army if they are not being press-ganged into slavery.