In 1917, Kazan became one of the revolution centers, Gunpowder Plant fire occurred in the city. In 1918, Kazan was a capital of the Idel-Ural State, which was suppressed by the Bolshevist government. In the Kazan Operation of August 1918, it was briefly occupied by Czechoslovak Legions. In 1920 (after the October Revolution), Kazan became the center of Tatar Autonomous Soviet Socialist Republic. In the 1920s and 1930s, most of the city's mosques and churches were destroyed, as occurred elsewhere in the USSR. During World War II, many industrial plants and factories to the west were relocated in Kazan, making the city a center of the military industry, producing tanks and planes. After the war, Kazan consolidated as industrial and scientific center. In 1979, the city's population reached the number of 1 million. Around this period the city was gripped by a moral panic in the form of the rise of juvenile delinquency and street gangs in what became known as the "Kazan phenomenon".