On 17 November 1989 (International Students' Day), riot police suppressed a student demonstration in Prague. The event marked the 50th anniversary of a violently suppressed demonstration against the Nazi storming of Prague University in 1939 where 1,200 students were arrested and 9 killed (see Origin of International Students' Day). The 1989 event sparked a series of demonstrations from 17 November to late December and turned into an anti-communist demonstration. On 20 November, the number of protesters assembled in Prague grew from 200,000 the previous day to an estimated 500,000. The entire top leadership of the Communist Party, including General Secretary Miloš Jakeš, resigned on 24 November. On 27 November, a two-hour general strike involving all citizens of Czechoslovakia was held.