Burgos- siege successful 1812

WI Wellington's seiege had worked instead of being the half-baked abortion that it was Aug- Oct 1812 ? How would the course of the Peninsular War have been affected ?
 
You'd probably see the Grand Army or it's equivilent deployed to either defend against an invasion of France or to remedy the situation on Iberia. Either way the invasion of Russia is done for. This actually could be a good thing for Napoleon.
 
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