In the early years of the 20th century, Minsk was a major centre for the worker's movement in Belarus. The 1st Congress of the Russian Social Democratic Labour Party, the forerunner to the Bolsheviks and eventually the CPSU, was held there in 1898. It was also one of the major centres of the Belarusian national revival, alongside Vilnius. However, the First World War significantly affected the development of Minsk. By 1915, Minsk was a battlefront city. Some factories were closed down, and residents began evacuating to the east. Minsk became the headquarters of the Western Front of the Russian army and also housed military hospitals and military supply bases.