In OTL Napoleon had his best chance for a decisive victory over the allies in 1813 at Bautzen.
http://en.wikipedia.org/wiki/Battle_of_Bautzen
So WI Napoleon succeeds in crushing the allies? Does he then revert to his grand strategy, advance on Berlin and then onto Danzig and the Vistula? What does Austria do? Does Austria jump in too save the allies, or are they sufficiently cowed? Does Russia sue for peace or fight on? Does the Tsar end up Napoleon's prisoner? What about the peninsula?
http://en.wikipedia.org/wiki/Battle_of_Bautzen
So WI Napoleon succeeds in crushing the allies? Does he then revert to his grand strategy, advance on Berlin and then onto Danzig and the Vistula? What does Austria do? Does Austria jump in too save the allies, or are they sufficiently cowed? Does Russia sue for peace or fight on? Does the Tsar end up Napoleon's prisoner? What about the peninsula?