 Complete the following phrase:  During the industrialisation of Prussia, Dortmund became a major centre for coal and steel. The town expanded into a city, with the population rising from 57,742 in 1875 to 379,950 in 1905. Sprawling residential areas like the North, East, Union and Kreuz district sprang up in less than 10 years. In 1920, Dortmund was one of the centres for resistance to the Kapp Putsch - a right military coup launched against the Social Democratic-led government. Radical workers formed a Red Army who fought the freikorps units involved in the coup. On 11 January 1923, the 