 In December 1812, temperatures in Vilnius had sunk to −30°C, and the frozen ground made proper burials impossible.The Grande Armée at that time comprised French, Portuguese, Italians, Germans, Austrians, Spaniards, and Croats, as well as Lithuanians and Poles.The bones have been intensively studied by forensic pathologists; DNA evidence showed that many of the deaths were caused by typhus.