The armed police stand in front of a monument marking "Mukden Incident", or September 18 Incident of 1931, at the "9.18" Historical Museum in Shenyang, capital of Northeast China's Liaoning province, Sept 17, 2011. Three provinces in Northeast China - Heilongjiang, Jilin and Liaoning - ring alarm bells at the same time on Sunday to mark the 80th anniversary of the historical incident on Sept 18, 1931 which was the beginning of the Japanese military occupation of Northeast China, then known as Manchuria, until Japan surrendered on August 15, 1945. The museum is located on the site where the Japanese troops destroyed the South Manchuria Railway, which was used as an excuse to invade China.