Sixth Fleet (Imperial Japanese Navy)

Sixth Fleet (Imperial Japanese Navy). The Sixth Fleet was the primary submarine warfare command of the Imperial Japanese Navy, established in 1940 and active throughout the Pacific War. Primarily composed of long-range fleet submarines, it was tasked with reconnaissance, commerce raiding, and engaging major enemy capital ships. Despite early successes, its operational effectiveness was hampered by doctrinal limitations and increasingly effective Allied anti-submarine warfare as the war progressed.

History

The Sixth Fleet was officially formed on 15 November 1940, consolidating the Imperial Japanese Navy's submarine forces under a single operational command. Its creation reflected the growing importance of submarines in Japanese naval strategy prior to the outbreak of the Pacific War. The fleet's headquarters was established at the Yokosuka Naval District, with forward bases later developed at Kwajalein Atoll, Truk Lagoon, and Rabaul. Following the attack on Pearl Harbor, the Sixth Fleet played a significant role in early operations, including reconnaissance missions and attempts to interdict United States Navy forces. However, its strategic impact waned after the pivotal Battle of Midway, where its submarines failed to significantly affect the outcome. The fleet was formally disbanded with the dissolution of the Imperial Japanese Navy following the surrender of Japan.

Organization

The organizational structure of the Sixth Fleet was centered around submarine squadrons, known as *Sentai*, which were typically composed of multiple divisions. Key subordinate commands included Submarine Squadron 1, Submarine Squadron 2, Submarine Squadron 3, and Submarine Squadron 7, each controlling a varying number of boats. The fleet also commanded specialized units such as the Submarine Division 11, which operated midget submarines like those used at Pearl Harbor, and the 8th Submarine Squadron, which was active in the Indian Ocean. Support and tender vessels, such as those from the Yokosuka Naval District, provided logistical backing for extended patrols. This structure allowed for deployment across vast areas of the Pacific Ocean, from the Aleutian Islands to the coast of Madagascar.

Submarine operations

Doctrinally, the Sixth Fleet primarily employed its submarines in direct support of the Combined Fleet, focusing on fleet-on-fleet engagements rather than commerce raiding against merchant shipping. Early-war operations included advance scouting for the Kidō Butai and patrol lines intended to ambush United States Navy aircraft carriers. Notable individual actions included the sinking of the USS Wasp (CV-7) by I-19 near Guadalcanal and the damaging of the USS Saratoga (CV-3) by I-26. Submarines also conducted clandestine missions, such as supply runs to isolated garrisons, shelling of coastal targets like Ellwood Oil Field in California, and launching Yokosuka E14Y reconnaissance aircraft. However, these efforts were increasingly countered by sophisticated Allied sonar, radar, and coordinated destroyer tactics.

Commanders

Commanders-in-Chief of the Sixth Fleet were senior flag officers with extensive naval experience. The first commander was Vice Admiral Mitsumi Shimizu, who led the fleet during the attack on Pearl Harbor. He was succeeded by Vice Admiral Marumo Kuninori in March 1942. Later commanders included Vice Admiral Teruhisa Komatsu and Vice Admiral Takeo Takagi, who oversaw operations during the intense battles of the Solomon Islands campaign. The final commander was Vice Admiral Kiyohide Shima, who presided over the fleet's dissolution. Key staff officers often included veterans of the Naval War College (Japan) and previous commands within the Combined Fleet.

Notable engagements

The Sixth Fleet participated in several major campaigns, though with mixed results. Its submarines were deployed during the attack on Pearl Harbor, where five midget submarines failed in their attack. At the Battle of Midway, a submarine patrol line failed to intercept the United States Navy task forces. The fleet saw more success in the attritional battles around Guadalcanal, contributing to the Tokyo Express supply runs and scoring hits on major warships. Individual boats achieved notable sinkings in the Indian Ocean and off the coast of Australia, such as the work of I-165. However, the fleet was unable to stem the tide of the Allied advance or sever crucial logistics lines, culminating in its diminished role during the Battle of Leyte Gulf and the Battle of Okinawa.

Category:Imperial Japanese Navy fleets Category:Military units and formations established in 1940 Category:Military units and formations disestablished in 1945