On 15 August 1914, at the outbreak of World War I in Europe, Japan delivered an ultimatum to Germany demanding that it relinquish its control of the disputed territory of Kiaoutschou. Upon rejection of the ultimatum, Japan declared war on 23 August and the same day its navy bombarded the German territory. On 7 November 1914, the bay was occupied by Japanese forces (see Siege of Tsingtao). Following resolution of the Shandong Problem, the occupied territory was returned to China on 10 December 1922 but the Japanese again occupied the area from 1937 to 1945 during the Second Sino-Japanese War.