Maximum damage to Napoleon's army during his march to Moscow was done by?

Typhus REF: Battle of La Rothiere 1814 Napoleon marched into Russia in the summer of 1812 with a half-million soldiers. Only a few thousand staggered out again, victims of war, weather, and disease. Using dental pulp extracted from the teeth of soldiers who died during Napoleon's disastrous retreat through Russia in 1812, a new study finds DNA evidence that epidemic typhus and trench fever ran rampant among the French Grand Army. The study, published in the Jan. 1 issue of The Journal of Infectious Diseases, identifies the specific species of louse-borne pathogens that were a major cause of death among the remains of the retreating army. The team analyzed dental pulp from 72 teeth, taken from the remains of 35 soldiers. Dental pulp from seven soldiers contained DNA from B. quintana, and pulp from three soldiers contained DNA from Rickettsia prowazakii, which causes epidemic typhus