In 1938, the Japanese 19th Division entered territory claimed by the Soviet Union, leading to the Battle of Lake Khasan. This incursion was founded in the Japanese belief that the Soviet Union misinterpreted the demarcation of the boundary, as stipulated in the Treaty of Peking, between Imperial Russia and Manchu China (and subsequent supplementary agreements on demarcation), and furthermore, that the demarcation markers were tampered with.