Anti-Japanese racism and the belief in the Yellow Peril in California intensified after the Japanese victory over the Russian Empire during the Russo-Japanese War. On 11 October 1906, the San Francisco, California Board of Education passed a regulation in which children of Japanese descent would be required to attend racially-segregated separate schools. Japanese immigrants then made up approximately 1% of the population of California, and many of them had come under the treaty in 1894 which had assured free immigration from Japan.