The most virulent source of the unfolding tragedy was cloaked, invisible to the eyes of the army’s leaders.

From The Illustrious Dead by Stephan Talty.  Page 96.

Cossacks and villagers were certainly attacking foraging parties, but the main body of Russian troops was in full retreat and in no position to mount operations. These minor skirmishes were in no way as lethal to his men as sickness was, and one wonders at his information, or his interpretation of it. First Larrey had blamed rotten cognac. Now Napoleon blamed marauders, who were certainly killing his soldiers but not in the massive numbers that were actually being lost. Miscommunication was masking the real problem. The most virulent source of the unfolding tragedy was cloaked, invisible to the eyes of the army’s leaders.

The misdiagnosis was potentially significant. Mistakes in the foragers’ protection could be corrected: more squads sent out and discipline enforced on the distribution of the provisions. But an epidemic of typhus couldn’t be stopped by his medical authorities. Other armies in the past faced with the pathogen had retired from the field whenever possible and taken up the campaign when the epidemic had passed. Had Napoleon known (or acknowledged to himself) the true reason for the astonishing casualty rate, he might have considered a winter rest in Smolensk.