FORT IV Stanisław Żółkiewski (Graf Ludwig Yorck von Wartenburg). An artillery fort built in the years 1878-1884 of brick, on a pentagonal plan, as the main artillery fort of the Biehlers' type, protected the Toruń Mokre and Toruń Północ railway stations. It could survive a six-month siege. It was intended for a crew of two infantry companies and the service of artillery positions (totalling about 800 people), accommodated in 31 residential rooms. The armament of the facility consisted of 14 medium-caliber guns and, at various times, from 15 to 22 heavy-caliber guns located in two wing batteries together with shelters for their crews. A casemate and 9 infantry shelters have been preserved on the fort's premises. In the 1890s and in the years 1911–1914 it underwent modernization: some windows were bricked up, the rest were equipped with armoured shutters, ammunition elevators were eliminated due to the artillery being moved to coupled batteries, mechanical ventilation was introduced. The whole was surrounded by barbed wire. Part of the barracks and the postern were reinforced, which made the vital parts of the fort resistant to shells from 220 mm cannons.