|Pre-War aerial photograph of the fortress. |
During the Invasion of Poland at the beginning of the Second World War, Modlin Fortress was a headquarters of the Modlin Army until it retreated eastwards. From September 13 to September 29, 1939 it was defended by Polish forces under the command of general Wiktor Thommée against assaulting German units. During that time, the fighting was closely connected with the strategic situation of the Battle of Warsaw.
Among Polish forces defending the fortress was the armoured train 'Śmierć' (death). Modlin anti-aircraft battery was the one that shot down the most Luftwaffe planes in September. Modlin capitulated on September 29, as one of the last Polish units to remain operational during the campaign.