mostly by small farms and windmills (mills being the namesake of Wola's central neighborhood Młynów) to an industrial and manufacturing centre. Metallurgical, textile and glassware factories were commonplace, with chimneys dominating the westernmost skyline. Like London, Warsaw's population was subjected to income segmentation. Gentrification of inner suburbs forced poorer residents to move across the river into Praga or Powiśle and Solec districts, similar to the East End of London and London Docklands. Poorer religious and ethnic minorities such as the Jews settled in the crowded parts of northern Warsaw, in Muranów. The Imperial Census of 1897 recorded 626,000 people living in Warsaw, making it the third-largest city of the Empire after St. Petersburg and Moscow as well as the largest city in the region. Grand architectural complexes and structures were also erected in the city centre, including the Warsaw Philharmonic, the Church of the Holiest Saviour and tenements along Marszałkowska Street. During World War I, Warsaw was occupied by Germany from 4 August 1915 until November 1918. The Armistice of 11 November 1918 concluded that defeated Germany is to withdraw from all foreign areas, which included Warsaw. Germany did so, and underground leader Józef Piłsudski returned to Warsaw on the same day which marked the beginning of the Second Polish Republic, the first truly sovereign Polish state after 1795. In the course of the Polish–Soviet War (1919–1921), the 1920 Battle of Warsaw was fought on the eastern outskirts of the city. Poland successfully defended the capital, stopped the brunt of the Bolshevik Red Army and temporarily halted the "export of the communist revolution" to other parts of Europe. The interwar period (1918–1939) was a time of major development in the city's infrastructure. New modernist housing estates were built in Mokotów to de-clutter the densely populated inner suburbs. In 1921, Warsaw's total area was estimated at only 124.7 km2 with 1 million inhabitants–over 8,000 people/km2 made Warsaw more densely populated than contemporary London. The Średnicowy Bridge was constructed for railway (1921–1931), connecting both parts of the city across the Vistula. Warszawa Główna railway station (1932–1939) was not completed due to the outbreak of the Second World War. Stefan Starzyński was the Mayor of Warsaw between 1934 and 1939. Second World War After the German Invasion of Poland on 1 September 1939 started the Second World War, Warsaw was defended until 27 September. Central Poland, including Warsaw, came under the rule of