The occupation period is a heroic and dramatic card in the history of PWPW. The building of the company became the shelter for "Agaton" – a troop of the Home Army composed of the employees of PWPW who secretly produced banknotes and legalisation documents for the needs of the Polish Underground State. After the outbreak of Warsaw Uprising, the employees of PWPW recaptured the building from the hands of the Germans and were determinedly defending it from the attacks of the Nazi for nearly one month. In the history of Warsaw, the building of PWPW is known as one of insurgent redoubts of the Old Town.
On 27 August 1944, 1600 Nazi soldiers (supported by armour) eventually attacked the building defended at that time by as few as 200 insurgents. After pitched battle for every floor of the building in Sanguszki Street, on 28 August 1944, the insurgents left the building.
During 27 days of the fights, almost 100 insurgents were killed in the building.