Russian Red Army troops started occupying Włocławek on 20th January 1945. Immediately afterwards, the new power structures and state administration were established in the city. Włocławek was once again part of the Pomeranian Voivodeship – and in 1950 the Bydgoszcz Voivodeship. After the World War II the economy was completely ruined, and the city's population dropped by almost half. Communists nationalized most of the industry. However, this did not have a positive impact on the state of the economy because the development was characterized by a lack of dynamism.
The second half of the 1960s and the 1970s was an important period in the city's economic development. The construction of the waterworks on the Vistula River, the opening of the factory the “Włocławek” Nitrogen Plant /in Polish: Zakłady Azotowe „Włocławek”/ as well as the modernization of existing factories were the most important industrial investments in the city.
A modern library building was also built on Warszawska Street, together with new railway and bus station. The construction of new industrial plants was accompanied by the building of housing estates - Zazamcze, Kazimierza Wielkiego and Południe districts. After the administrative reform of the country in 1975, Włocławek was promoted to the status of a provincial town and its administrative functions were extended to the territory of two regions: Eastern Kuyavia and the Dobrzyń Land. Administrative institutions were established, and communal institutions were created from scratch. By the 1980s the population of Włocławek had risen to 130,000 inhabitants.
Despite much investment and financial outlay, the communist economic system, based on flawed assumptions, was becoming increasingly inefficient. From the mid-1970s, economic crisis and massive protests grew in Poland. As a result of the repressive actions of the authorities, society responded by forming an anti-communist opposition, in which anti-authoritarian independent trade union movement ‘Solidarity’ (in Polish: NSZZ Solidarność) played a major role. In the 1980s, Włocławek was the scene of numerous demonstrations and strikes organized in response to the oppressive actions of the communist state authorities. The years of the Martial Law state in Poland between 1981 and 1983 were particularly difficult for the town and its inhabitants.
Włocławek is also known as the scene of the tragic death of Jerzy Popiełuszko, priest and chaplain associated with opposition’s ‘Solidarity’ movement. He was murdered in 1984 by three agents of the Security Service of the Ministry of Internal Affairs (in Polish: Służba Bezpieczeństwa). The era of communism came to an end in the city with the first partially-free parliamentary elections on June 4, 1989. This was the first major step in the fall of communism both in Poland and other countries of Central-Eastern Europe.
