"My cavalry is in tatters, many horses are dying," dictated Napoleon, the once-feared leader showing the strain of his calamitous Russian invasion, which halved his army.
The rare document -- dated Oct. 20, 1812, signed "Nap" in the emperor's hand and written in numeric code -- is up for auction Sunday at France's Fontainebleau Auction House.
The Napoleon code, used only for top-secret letters when the French emperor was far from home, aimed to stop enemies from intercepting French army orders.
The code was regularly changed to prevent it from being cracked.
