He was a member of the Sejm in 1809. During the Austro-Polish War, he organized secret patriotic activities. When Napoleon's armies took Vilnius, he became a member of the Armed Forces Committtee of the Lithuanian Provisional Governing Commission. Appointed a Colonel, he created his own regiment and became an Adjutant to General . In 1812, he was sent to Warsaw, then spent eleven months in the besieged Modlin Fortress. After its surrender by General Herman Willem Daendels, Chodkiewicz refused to cooperate, and was taken prisoner by the Russians for a brief period.