After the disastrous retreat of Napoleon's army, and while recovering from his injuries, Poniatowski quickly undertook the rebuilding of the Polish army in order to replace the forces devastated by the Moscow campaign. When many Polish leaders began to waver in their allegiance to the French Emperor, Poniatowski resisted this change of opinion and remained faithful to Napoleon, even when Tsar Alexander I offered him amnesty and proposed future cooperation. With the new army only partially completed, on 5 February, as the Russian army was about to enter Warsaw, the Polish units moved out, not sure of their immediate purpose. Eventually they reached Kraków, where they stayed for a few weeks getting ready.