Unraveling Japan’s Submarine Assault on Pearl Harbor

The attack on Pearl Harbor that brought Japan and the United States into World War II was not only a surprise aerial assault but also involved a significant presence of submarines. This article delves into the details of Japan’s submarine fleet deployed to the Hawaiian naval base, uncovering the role they played in the attack and their impact on the outcome of the operation.

The Japanese Submarine Fleet

Stretching from the Pacific Ocean to the waters off the coast of Japan, the Imperial Japanese Navy (IJN) operated a vast submarine fleet during World War II. However, the number and types of submarines that participated in the Pearl Harbor attack were quite limited. The operation involved a total of twelve submarines: six large Fleet submarines and six smaller midget submarines. These vessels were critical in ensuring the success of the strategic strike on the United States' Pacific fleet.

The Fleet Submarines

Long-Range and Strategic Assets

The Fleet submarines, also known as Type-96 submarines, were designed for long-range missions and could carry a significant payload of torpedoes. Six of Japan's largest submarines, type I-H and I-M, were assigned to the Pearl Harbor attack. Despite their size and advanced technology, these submarines were not able to penetrate the torpedo nets protecting Pearl Harbor, which is why they did not launch their main attack.

The Midget Submarines

Stealth and Ambition

Japan's midget submarines, or Type A Ko-hyoteki, were much smaller than the Fleet submarines. These submarines were designed for stealth and were intended to approach the harbor undetected. Additionally, they were equipped with smaller torpedoes and bomb launchers, making them ideal for destroying specific targets within the restricted area of Pearl Harbor. The midget submarines were part of the Kōshō Unit, which also included six midget submarines and two Katsura-class midget submarines.

Reasons for Deployment

The primary reason for deploying the midget submarines was to conduct internal attacks on the Pearl Harbor base, penetrating the torpedo nets and launching torpedoes directly into the ships. However, these submarines faced significant challenges. They were initially delayed in their transit to Pearl Harbor, and when they finally arrived, they had to operate in an area already heavily fortified by the US Navy.

The Attack Execution

The Role of the Midget Submarines

On the morning of December 7, 1941, the Kōshō Unit consisting of six Type A midget submarines and the two Katsura-class vessels were launched towards Pearl Harbor. The midget submarines followed a pre-planned route through a predetermined channel and were infiltrated into the harbor's anti-torpedo net. However, despite successfully entering the harbor, the midget submarines suffered from several technical and operational issues.

The attack was not as effective as planned. While one midget submarine managed to launch a single torpedo against the USS Oklahoma, the event was too late to have a significant impact on the fleet’s mobility. Another midget submarine was damaged by an anti-torpedo net, and one was driven aground by the US coast defense guns. Additionally, the third midget submarine sank after colliding with the USS Ward, while the fourth midget submarine, after launching two torpedoes at the USS Utah, did not hit its target. The fifth and sixth midget submarines reached their targets, but neither their attacks nor the hit on the USS Mindanao resulted in major damages.

The Fleet Submarines’ Involvement

The Fleet submarines, though not able to penetrate the anti-torpedo nets, were tasked with external attacks on Pearl Harbor’s perimeter. They conducted surveillance and restricted US naval movements by shelling the channel entrance towards Oahu. However, the effectiveness of their attacks was limited by their inability to approach the harbor without being detected by the US Navy’s alertness.

Impact and Aftermath

Operational and Efficacy Critique

The attack by Japan’s submarines, while a display of their technological and strategic capabilities, was largely ineffective in achieving a significant tactical advantage. The midget submarines, in particular, were compromised by operational and technical issues, and the Fleet submarines were unable to break through the harbor’s defenses.

However, the psychological impact of this unconventional attack was immense. Japan’s objective to sow fear and confusion among the Americans was partially successful. The entry of the midget submarines into the harbor was a rare and unprecedented event that left a lasting impact on the public and military psyche.

Conclusion

The submarine assault on Pearl Harbor, involving both Fleet and midget submarines, remains a critical topic in naval history. Despite the challenges faced by the Japanese forces, their use of submarine tactics showcased the evolving nature of naval warfare in the mid-20th century. The lessons learned from this attack continue to influence modern naval strategies and submarine operations.

References

1. Ruether, Nicholas A. "Japanese submarines in World War II: A study of their deployment, employment, and effectiveness in fleet, special, and submarine operations." Naval History Department, 1988.

2. Wilmott, H.P. "The Battle of the Pacific: The War with Japan Part 1-3." Macdonald Janes, 1971.

3. Evans, David C., and Mark R. Peattie. "Kaigun: Strategy, Tactics, and Technology in the Imperial Japanese Navy, 1887-1941." Naval Institute Press, 1997.