The article describes formation of Lithuanian army units and their participation in the war in 1812-1814. In the second half of 1812 Napoleon established local administration in Lithuania and told ir to establish army units and regular army, which was subordinate to the direction of the French army. The war committee and the commission of government formed gendarmerie; national guard, militia units and regular army in towns under control of Lithuanian governor-general assigned by France. The purpose was to form five infantry regiments, two foot jaegers regiments, seven cavalry regiments, one squadron and one horse artillery regiment, but this formation was stopped by a commotion in the country and were not finished. Such Lithuanian units together with French forces had to protect the straggled rear of the great army from enemy troops coming from southeast. They took part in the Koidanov battle near Minsk, helped the main forces crossing the Berezina river, and defended Vilnius. The losses suffered in November – December, 1812, were catastrophically high. Later the 17th and 19th uhlan troops, 18th, 20th and 21st infantry troops acted as separate military unit. Other retreated Lithuanian troops joined Polish troops and fought together on the side of Napoleon until 1814, but they didn’t lose their names. When they came back to the territory of Poland (to join the ranks of foreign state recruits), regular troops made less than a quarter of soldiers, which was at the beginning of 1813, when they moved from Lithuania.