By the time of Napoleon's invasion of Russia in 1812, the III Corps had been reorganized and went under the command of Marshal Michel Ney. It consisted of a mixture of Croatian, French, Portuguese, Dutch and Württemberger units and like the rest of Napoleon's forces, suffered heavy casualties as the campaign progressed. At the crossing of the Niemen River in 1812, the size of the corps was estimated at around 44,000 men; by the Battle of Smolensk, only 22,000 men remained.