The was a major

navy base A naval base, navy base, or military port is a military base, where warships and naval ships are docked when they have no mission at sea or need to restock. Ships may also undergo repairs. Some naval bases are temporary homes to aircraft that us ...

for the

Imperial Japanese Navy The Imperial Japanese Navy (IJN; Kyūjitai: Shinjitai: ' 'Navy of the Greater Japanese Empire', or ''Nippon Kaigun'', 'Japanese Navy') was the navy of the Empire of Japan from 1868 to 1945, when it was dissolved following Japan's surrender ...

in central Japan during

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...

. Located at

Osaka is a designated city in the Kansai region of Honshu in Japan. It is the capital of and most populous city in Osaka Prefecture, and the third most populous city in Japan, following Special wards of Tokyo and Yokohama. With a population of 2. ...

), Osaka Guard District was responsible for guarding the approach to the old capital of

Kyoto Kyoto (; Japanese: , ''Kyōto'' ), officially , is the capital city of Kyoto Prefecture in Japan. Located in the Kansai region on the island of Honshu, Kyoto forms a part of the Keihanshin metropolitan area along with Osaka and Kobe. , the ci ...

, the Kansai industrial zone, port of

Kobe Kobe ( , ; officially , ) is the capital city of Hyōgo Prefecture Japan. With a population around 1.5 million, Kobe is Japan's seventh-largest city and the third-largest port city after Tokyo and Yokohama. It is located in Kansai region, whic ...

and the

Inland Sea An inland sea (also known as an epeiric sea or an epicontinental sea) is a continental body of water which is very large and is either completely surrounded by dry land or connected to an ocean by a river, strait, or "arm of the sea". An inland se ...

of Japan.

History

The were considered second tier naval bases, similar to the first tier , with docking, fueling and resupply facilities, but typically lacked a shipyard or training school. They tended to be established by strategic waterways or major port cities for defensive purposes. In concept, the Guard District was similar to the

United States Navy The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage ...

Sea Frontiers concept. the Guard District maintained a small

garrison A garrison (from the French ''garnison'', itself from the verb ''garnir'', "to equip") is any body of troops stationed in a particular location, originally to guard it. The term now often applies to certain facilities that constitute a mil ...

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. Osaka, a strategic port city and location of several shipyards was initially ranked as a third echelon naval port or reporting to the

Kure Naval District was the second of four main administrative districts of the pre-war Imperial Japanese Navy. Its territory included the Seto Inland Sea, Inland Sea of Japan and the Pacific Ocean, Pacific coasts of southern Honshū from Wakayama prefecture, Wakayam ...

. The military base itself was established in 1939, but was little more than a base in name only, and was intended to form an administrative structure as legal representative of the Imperial Japanese Navy in the Osaka area. It lacked in any base facilities, not even a repair yard, fueling depot or stores, and it relied on civilian-owned port facilities to service passing warships. Nonetheless, it was raised to the status of Guard District on March 13, 1940.

Order of Battle at time of the attack on Pearl Harbor

*Osaka Guard District *Komatsujima Air Group ** 8 ×

Nakajima E8N The Nakajima E8N was a Japanese ship-borne, catapult-launched, reconnaissance seaplane of the Second Sino-Japanese War. It was a single-engine, two-seat biplane with a central main-float and underwing outriggers. During the Pacific War, it was k ...

Dave ** 8 ×

Kawanishi E7K The Kawanishi E7K was a Japanese three-seat reconnaissance seaplane mainly in use during the 1930s. It was allocated the reporting name Alf by the Allies of World War II. Design and development In 1932 the Imperial Japanese Navy requested the K ...

Alf *Osaka Guard Force *Kii Defense Unit *Minesweeper Division 32 (''Eguchi Maru'', ''Senyu Maru No. 2'', ''Takashima Maru'')

List of commanders

Commanding Officer

*Vice-Admiral Masashi Kobayashi (20 Nov 1941 – 9 Mar 1943) *Vice-Admiral Kakusaburo Makita (9 Mar 1943 – 1 Apr 1944) *Vice-Admiral Ichiro Ono (1 Apr 1944 – 1 Nov 1944) *Vice-Admiral Arata Oka (1 Nov 1944 – 30 Nov 1945)

Chief of Staff

* Rear-Admiral Shinichi Torigoe (20 Nov 1941 – 13 Aug 1943) * Rear-Admiral Bunjiro Yamaguchi (13 Aug 1943 – 26 Feb 1945) * Rear-Admiral Akira Maysuzaki (26 Feb 1945 – 30 Nov 1945)