He was made the commander of the Brześć Fortress and managed to organise resistance against the advancing German XIX Panzer Corps of general Heinz Guderian.

After the unconcluded Battle of Brześć, in which his four infantry battalions managed to halt the advance of four German divisions for four days, Plisowski retreated with his men and joined the forces of general Franciszek Kleeberg.

On 24 September he was made the commanding officer of the Nowogródzka Cavalry Brigade, with which he fought both against Nazi Germany and the Soviet Union.

On 28 September 1939 Plisowski was taken prisoner of war by the Soviets and sent to the Special NKVD Interrogation Camp for Polish PoWs in Starobielsk.

The victims of the Katyn Massacres include 20 or so Polish generals, among whom Leon Billewicz, Stanisław Haller, Aleksander Kowalewski, Kazimierz Łukoski, Franciszek Sikorski, Leonard Skierski, Piotr Skuratowicz were murdered at the same location as Pilowski.