Ostasiengeschwader
In August 1914, Yamaya was assigned to command the South Seas Squadron (consisting of the cruisers , and ) upon the outbreak of World War I patrolling for German warships of German East Asia Squadron in the South Pacific from October to December 1914. Under his command, Japanese forces occupied the former German colonies of Yap and the Caroline Islands. He was awarded the Navy Distinguished Service Medal by the United States government for his contributions to the Allied effort in World War I.