 Complete the following phrase:  Pilecki was mobilized as a cavalry platoon commander on 26 August 1939. He was assigned to the 19th Infantry Division under General Józef Kwaciszewski, part of the Polish Army Prusy and his unit took part in heavy fighting against the advancing Germans during the invasion of Poland. The 19th Division was almost completely destroyed following a clash with the German forces on the night of 5 to 6 September at the battle of Piotrków Trybunalski. Its remains were incorporated into the 41st Infantry Division, which was withdrawn to the southeast toward Lwów now Lviv in Ukraine and the Romanian bridgehead. In the 41st Division, Pilecki served as divisional second-in-command of its cavalry detachment, under Major Jan Włodarkiewicz. He and his men destroyed seven German tanks, shot down one aircraft, and destroyed two more on the ground. On 17 September, the 