Horseshoe.

This is coolbert:

From the PBS television series "Bullets, Boots and Bandages"and thanks to the BBC we have this most interesting item.

"Napoleon's failure: For the want of a winter horseshoe"

That army of Napoleon retreating from Moscow [1812] having their horse transport reduced to near zero, the animals as shod with the wrong horseshoes, organized transport in the traditional and normal manner of that period made negligible.

"Of all the challenges faced by generals through history, moving armies has been one of the greatest - and Napoleon Bonaparte's invasion of Russia 200 years ago illustrates just how badly things can go wrong when it is underestimated".

"Having entered Russia in June, and anticipating a short campaign, his [Napoleon] horses were still shod with summer shoes."

"But with the brutal Russian winter fast approaching, this tiny logistical oversight was to cost him dear. Winter horseshoes are equipped with little spikes that give a horse traction on snow and ice, and prevent it from slipping."

"Without them, a horse can neither tow a wagon uphill, nor use them as brakes on the way down."

There not being enough farriers [those craftsmen that shoe horses] and proper numbers of spiked horseshoes to fit the horses to begin with. An unanticipated calamity without mitigation the result.

During that period of the American Civil War an army of 100,000 men  requiring about 2,500 wagon loads of supply per day for sustainment, not even during conditions of battle!! WAGONS OF COURSE PULLED BY HORSES!

Fodder for the horses during the extreme cold of the Russian winter being nil, campaigns typically during the Napoleonic era [and that time of the American Civil War for that matter] traditionally ceasing during that time of cold!!

coolbert.