In April 1811 Poniatowski went to Paris, where he represented the King of Saxony and Duke of Warsaw Frederick Augustus I at the baptism ceremonies of Napoleon's son. He stayed there for four months and worked with the Emperor and his generals on plans for the campaign against Russia. He tried to convince the French leaders that the southern route, through the current day Ukraine would provide the most benefits. Not only was the region warmer, Polish gentry from the Russian partition would join in, and possible Turkish action against Russia could be supported, which was the most advantageous theater for the upcoming war. Napoleon rejected the idea, as well as the back-up scenario, according to which Poniatowski would follow such a route alone with the Polish corps, hoping to take over these formerly Polish areas with the expected help from a Polish uprising planned there. For the Russian Campaign of 1812 Poniatowski became commander of V Corps of the Grande Armée — at nearly 100,000 strong Polish forces in the Grande Armée were the greatest Polish military effort before the 20th century.