During the Battle of Somosierra, Kozietulski was the commander who led the Polish cavalry against the Spanish artillery and infantry. Although not the only commander present during the charge, he was credited with the victory after the battle and in Poland remains the best-known veteran of that campaign. He was also one of 18 Poles to be awarded the French Legion of Honour after the battle. Following the Peninsular War Kozietulski remained in the military and distinguished himself in the Battle of Wagram, where he led the Polish cavalry unit against other Polish cavalry units fighting alongside the Austrians. For his merits, in 1811 he became a baron of the empire.