The Ryojun Guard District (旅順要港部, Ryojun Yōkōbu) was the major navy base for the Imperial Japanese Navy in the Kwantung Leased Territory before and during Second Sino-Japanese War. Located in at Ryojun 38°48′45″N 121°14′30″E / 38.81250°N 121.24167°E / 38.81250; 121.24167), (present-day Lüshunkou, China, The Ryojun Guard District was responsible for control of the strategic seaward approaches to Manchukuo and to north China and for patrols in the Yellow Sea and along the China coastlines. It was disbanded in 1943.

The Guard Districts (警備府, Keibifu) were second tier naval bases, similar to the first tier Naval Districts (鎮守府), with docking, fueling and resupply facilities, but typically lacked a shipyard or training school.^[1] They tended to be established by strategic waterways or major port cities for defensive purposes.^[2] In concept, the Guard District was similar to the United States Navy Sea Frontiers concept. the Guard District maintained a small garrison force of ships and Naval Land Forces which reported directly to the Guard District commander, and hosted detachments of the numbered fleets on a temporary assignment basis.

The port of Ryojun on the Kwantung Peninsula was an area with a long association with the Imperial Japanese Navy, having been first seized during the First Sino-Japanese War in December 1894. Japan was forced to abandon the port due to the Triple Intervention in February 1896, and its port facilities were soon occupied and developed by the Imperial Russian Navy as Port Arthur, Russia's most important naval base in the Far East.

The Russian naval base was seized by Japan after the Battle of Port Arthur in August 1904 and was proclaimed the Ryojun Naval District (龍順鎮守府). However, it lacked the shipyards, armories and the training facilities associated with other naval districts, (for which it relied on Sasebo Naval District). Tasked primarily with coastal patrols of the Liaodong Peninsula and control of the strategic seaward approaches to Tianjin and Beijing, it was regarded as a prestigious posting, with its commander receiving his commission directly from the Emperor.

However, on March 14, 1914, the status of the Ryojun Naval District was reduced to that of a third echelon naval port, or yōkōbu (要港部). It served as a staging point and refueling base in World War I for operations against the Imperial German Navy’s East Asia Squadron based out of Qingdao. With the Allied victory in World War I eliminating the German threat and with the Washington Naval Treaty limiting naval forces, Ryojun Military Port was deactivated on December 1, 1922.

In April 1933, the base was reactivated, and its role expanding to include patrols and guard of the coastline of Manchukuo. On November 20, 1941, in anticipation of the coming war with the United States, Ryojun was upgraded to Guard District status.

However, on January 15, 1942, with Japan in full control of the seaward approaches to China and Manchukuo, the Guard District was again deactivated.

• Ryojun Guard District
• Minesweeper Division 32
  • Shanan Maru #16

Commanding officer^[3]

Chief of Staff^[3]

• Prados, John (1995). Combined Fleet Decoded: The Secret History of American Intelligence and the Japanese Navy in World War II. Annapolis: Naval Institute Press. ISBN 0-460-02474-4.
• Goldstein, Donald M (2004). The Pacific War Papers. Brassey. ISBN 1-57488-632-0.

• Wendel, Marcus. "Axis History Database".
• Budge, Kent G. "Pacific War Online Database".