The city of Tashkent began to industrialize in the 1920s and 1930s, but industry increased tremendously during World War II, with the relocation of factories from western Russia to preserve the Soviet industrial capacity from the hostile invading Nazis. The Russian population increased dramatically as well, with evacuees from the war zones increasing the population to well over a million. (The Russian community would eventually comprise more than half of the total residents of Tashkent by the 1980s.) On 26 April 1966, Tashkent was destroyed by an earthquake and over 300,000 were left homeless. At the time of the collapse of the Soviet Union in 1991, Tashkent was the fourth largest Soviet city and a major center of learning in the fields of science and engineering.