Sasebo Naval District

The location of Sasebo 33°10′05″N 129°44′06″E facing China and Korea, and near the foreign treaty port of Nagasaki was recognized of strategic importance by the leaders of the early Meiji government and early Imperial Japanese Navy. In 1883, the then Lieutenant Commander Tōgō Heihachirō nominated what was a tiny fishing village as the ideal location for a naval base. With the formation of the navy in 1886, Japan was divided into five Naval Districts (海軍区) each with a headquarters (鎮守府). Sasebo was designated as the "Third Naval District" (第三海軍区, dai-san kaigunku), and its harbor was dredged, a breakwater constructed and docking, coaling and repair facilities for warships were established, and the military base was officially opened in 1889. To stress the importance of the base, Emperor Meiji made a personal inspection tour in 1890.

The base was connected to the rest of Japan by rail in 1898, and the Sasebo Naval Arsenal, which would eventually expand to become one of the largest shipyards in Japan for the construction of smaller warships, began operation in 1903. As with the other Naval Districts, Sasebo was intended to operate as independently as possible, and facilities included armories, production factories for torpedoes, naval mines and naval artillery (and associated ammunition), and also a naval hospital and training centers. In concept, the Naval District was similar to the United States Navy Sea Frontiers concept. the Naval 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.

Sasebo was the closest ship repair facility for the Imperial Japanese Navy to the combat zones of the Russo-Japanese War and saw considerable activity during that conflict.

In 1920, the Japanese navy established an air wing and a wireless communications center in 1922. In 1934, the Tomozuru capsized off Sasebo with loss of most of its crew, and leaving behind serious questions about the basic design of many Japanese warships.

In 1941, base facilities were expanded considerably for the Pacific War. The base also hosted a major portion of the Japanese Special Naval Landing Forces. The Imperial Japanese Navy had some 60,000 people working in the dock yard and associated naval stations at the peak of World War II, outfitting ships, submarines and aircraft.

Most of the base was destroyed by American air raids on Japan on June 28, 1945. After the surrender of Japan, Sasebo was occupied by the U.S. Marine Corps' Fifth Division, and the Sasebo Naval District was formally abolished on November 30, 1945.

Part of the former base facilities is still in use by the United States Navy as the United States Fleet Activities Sasebo and by the Japan Maritime Self-Defense Force. One of the former base structures is now a museum.

• Third Naval District (Admiral Tanimoto)
  • AO Sata
  • Sasebo Naval Base
    • Base HQ
    • Communications
    • Supply
    • Accounting
    • Construction
    • Ports & Docks
    • Navy Yard
    • Navy Hospital
    • Navy Prison
    • Naval Fuel Depot
    • Base Garrison
    • Special Naval Landing Forces
  • Sasebo Submarine Base
  • Sasebo Air Group
    • 16x Mitsubishi A5M Claude
    • 6 x Aichi E13A Jake
    • 15 x Kawanishi H6K Mavis
  • Sasebo Guard Force
    • Sasebo Coastal Defense Squadron
      • PM Kozan Maru
    • Sasebo Local Defense Squadron
      • PG Shinkyo Maru (2672 tons)
      • PG Shinkyo Maru #5
    • Minesweeper Division 42
      • AMc Seki Maru (297 tons)
      • AMc Toshi Maru #7 (297 tons)
  • Oshima Guard Force (based at Naze, Oshima Island)
    • AMc Chuon Maru #8
    • AMc Hakata Maru #7 (257 tons)
    • AMc Himejima Maru
    • Minesweeper Division 41
      • AMc Kyo Maru #1
      • AMc Kyo Maru #3
      • AMc Kyo Maru #5

• 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.
• Order of Battle at start of Pacific War