What is Suigun?: The Unsung History and Role of the Suigun

The story of Japanese warriors that even Japanese people don’t know

Globally renowned Japanese anime like “One Piece” are inspired by pirates, but did you know Japan had its own version of them?
This article will focus on the Suigun, a presence that colored the history of Japan’s seas but were far more than simple plunderers.
Let’s unravel their little-known story, exploring how they emerged, what roles they played, and how they were tossed about by the waves of their era.

There’s a clear distinction between Japanese “kaizoku” (pirates) and Western “pirates.”
While Western pirates were groups that attacked ships and plundered goods without reason, Japanese naval forces like the Murakami kaizoku were groups with their own set of rules.

The term Suigun is relatively modern, coined and popularized by local historians in the early Showa period (around the 1920s).
This is thought to have been an effort to shake off the negative image of their ancestors as “bandits” and align with a more positive public perception of the Murakami clan.
However, older documents refer to them as “kaizoku.” The name “Suigun” was born after the Meiji era when military forces were organized, becoming the predecessor to the modern Kaigun (navy).
In recent years, cultural agencies like the Agency for Cultural Affairs have increasingly used the term “Murakami kaizoku.”
This is because the understanding has spread that Japanese pirates had a variety of roles, and “Suigun” only represents a part of that larger function.

This shift in terminology reflects a process of historical reinterpretation and social image management.
The initial use of “Suigun” was intended to elevate them from the negative “kaizoku” label to a military organization – the predecessor of the navy – and thereby enhance their legitimacy.
However, the renewed use of “kaizoku” today stems from a more complex understanding of their activities.
They weren’t just military forces; they had their own rules and played diverse roles as autonomous entities in areas beyond the reach of public authority.
This illustrates how historical terms change over time and how those changes can influence people’s perception of history.

The Rise and Evolution of the Suigun: The Birth of Sea Warriors

As an island nation, Japan, like its neighbor Korea, has had coastal residents known as Kaimin (sea people) serving as naval forces since ancient times.
During the era of the ancient Yamato state, sea clans like the Azumi clan, Amabe clan, and Tsumori clan supported Japan’s early naval forces.
The Osaka Bay and Seto Inland Sea were critical transportation routes, akin to the nation’s backbone. Powerful local clans, such as the Ki clan from the Kinokawa River basin, secured natural harbors and timber-producing hinterlands along the Seto Inland Sea, and they thrived by operating their own powerful naval forces.

In the Heian period, the historical record begins to mention “kaizoku,” who stole official goods transported by water. Initially, these were small groups, with orders to suppress pirates in the Seto Inland Sea issued during the Jogan era (859-879).
However, in the late Heian period, as powerful local figures gained influence, and just as land-based manor lords developed into the warrior class by making martial arts their profession, a class of sea warriors emerged who made fighting their profession.

Medieval pirates were not just plunderers.
They declared themselves to be Shinjin (divine people) serving the deities of the areas they patrolled, and they used this as a pretext to collect “hatsuhoryo” (first fruit offerings) and “jobun” (shares) from passing ships.
These were groups with military and economic power in a specific territory, similar to Yamabushi (mountain ascetics) and Akuto (villainous groups).
Merchant ships also acknowledged this system, for example, by slightly lowering their sails – a custom known as Reihan – when passing through a pirate’s checkpoint.
Medieval piracy, also known as Keigo-shu (guard groups), was carried out with a certain degree of social understanding, suggesting that they were not just outlaws but also played a role in maintaining order in maritime traffic.

From the late medieval period to the early modern period, Japanese naval forces underwent a major transformation.
Coastal local lords of the medieval period came together to form powerful maritime forces known as Kaizoku-shu (pirate groups), which existed throughout Japan in regions like Kyushu, the Seto Inland Sea, the Kii Peninsula, Ise Bay, and Edo Bay.
In addition to plundering, they established checkpoints at sea to collect tolls, such as Hobetsusen (sail money), and provided escort services for ships.
They ignored the control of public authorities like the Shogunate and operated as independent military forces at sea.
In the 14th century, during the Nanboku-cho Wars (period of Northern and Southern Courts), they intensified their activities by fighting on behalf of either the Northern or Southern courts.

During the Muromachi period, land-based power began to extend to the sea.
Shugo daimyo (provincial governors) organized the surrounding pirate groups into Keigo-shu (guard groups) and used them as their own naval forces.
This trend became even more pronounced during the Sengoku period (Warring States period).
Sengoku daimyo recognized the importance of naval power for their territorial expansion and actively worked to organize naval forces, incorporating guard groups into their vassalage.
For example, the Hojo clan granted fishing privileges to fishermen in exchange for their service as a naval force in times of conflict.
Their peacetime livelihood and wartime military role were two sides of the same coin.

Thus, early “kaizoku” who began as small groups stealing official goods evolved into “sea warriors” who called themselves “shinjin” and maintained order by collecting passage fees in specific sea lanes.
Finally, they became military organizations called “suigun” when they were incorporated by Sengoku daimyo.
This progression shows how they were gradually legitimized and integrated into the feudal power structure, transforming from mere plunderers to an indispensable part of the centralizing powers of the daimyo.
As their specialized maritime knowledge and military power became essential, their independence waned, but they exerted their abilities as part of a larger organization.

The Diverse Roles of the Suigun: The Professionals Who Ruled the Sea

The Suigun were far more than just maritime combat units.
They were professional groups who ruled the sea, leveraging their expertise and military power to fulfill a wide range of roles 1.

Military Activities: The Naval Power that Decided Battles

The most direct role of the Suigun was their military involvement in Sengoku period battles.
Attacks and support from the sea were a crucial factor in determining the outcome of land battles, making their existence indispensable to the Sengoku daimyo.
This era saw the deployment of massive ships called Atakebune, which carried dozens to hundreds of crew members, leading to large-scale naval battles where these behemoths clashed.
Japanese naval warships, a type of non-keeled Japanese-style ship (Wasan), were heavily fortified with shields and armed with powerful weapons like large firearms and cannons, enhancing their combat capabilities.
A prime example is the Tekkosen (iron-clad ship), which Oda Nobunaga ordered and Kuki Yoshitaka built.

Management of Maritime Traffic: Piloting and Escort Services

The Suigun’s job wasn’t just to fight.
They used their advanced navigational knowledge to act as Suisen annainin (pilots) in areas with strong currents like the Seto Inland Sea.
In exchange for a toll, they guided ships along safe routes, preventing them from running aground or being shipwrecked.
Similarly, in exchange for a fee, they also served as bodyguards, protecting ships from piracy.
This shows that they were not just plunderers but also had a role as maintainers of maritime order.

Economic Activities: Collecting Passage Fees (Hobetsusen and Robetsusen)

Just as land-based daimyo collected land tax (nengu) from farmers to support their vassals and military, the Suigun had their own sources of revenue.
For example, the main source of income for the Murakami Suigun was the passage fees and pilotage fees they collected from ships passing through the Seto Inland Sea.
These fees were called Hobetsusen (sail money) or Robetsusen (oar money), based on the number of sails or oars on a ship.
They established checkpoints at sea, operated as independent military forces, and collected these tolls to maintain and expand their organizations.

The Linchpin of Logistics and Transport: Moving Supplies and Troops

In the large-scale and prolonged military campaigns of the Sengoku period, the Suigun served as the linchpin of logistics, transporting troops and supplies.
When Oda Nobunaga attacked Ishiyama Hongan-ji, the Suigun assisted in transporting troops and supplies.
Furthermore, as Toyotomi Hideyoshi pushed for the unification of Japan, a system for the efficient transport of troops, provisions, and other materials was essential to support military operations across a vast territory, making the incorporation of the Suigun extremely important.
During the invasions of Korea (Bunroku-Keicho no Eki), the Japanese Suigun played a crucial role in a “land-sea coordinated strategy” by supplying war materials to the advancing land forces and cooperating in attacks.

That the Suigun functioned as a comprehensive maritime business entity, not just a military unit, indicates that they existed as an autonomous, parallel power within their sphere of influence.
They managed economic activities, collected taxes, and maintained order just as land-based daimyo did in their territories.
Their economic and political autonomy meant they had built and maintained their own social system in the unique environment of the sea during an era of a yet-to-be-established central authority.
This multifaceted function is what distinguishes Japan’s Suigun from Western pirates.

Renowned Naval Forces and Famous Battles

During the Sengoku period, famous naval forces existed in seas across Japan, and their actions significantly influenced the course of battles.

The Champion of the Seto Inland Sea: The Heyday and Actions of the Murakami Suigun

The Murakami Suigun (Murakami Pirates), who operated primarily in the Geiyo Islands in the western Seto Inland Sea, were known as the greatest pirates in Japan.
The progenitor of the Murakami Suigun is said to be Saburozaemon Yoshihiro Murakami, a pirate from Innoshima.
The Noshima Murakami clan, considered the main branch of the three Murakami families, was the largest force and is said to have been the most “pirate-like” group.
Their peak came during the era of Murakami Takeyoshi, whom the missionary Luis Frois called “the greatest pirate in Japan”.

The Murakami Suigun’s contributions stood out in several famous battles.

• Contribution to the Battle of Miyajima (1555)
  In the Battle of Miyajima, fought between Mori Motonari and Sue Harukata for control of the Chugoku region, the Noshima Murakami Suigun sided with the Mori clan.
  They defeated Sue’s naval forces and significantly contributed to Mori’s dramatic victory.
  This battle is a symbolic example of the importance of naval warfare.
• The Siege of Ishiyama Hongan-ji and the First Battle of Kizugawaguchi (1576)
  In the conflict between Oda Nobunaga and Ishiyama Hongan-ji, the Murakami Suigun joined forces with Mori Terumoto, acting as part of the Mori naval forces to transport provisions to Hongan-ji.
  The Mori naval forces (about 800 ships) led by Murakami Motokiyo soundly defeated Oda Nobunaga’s naval forces (300 ships), and this battle established the Mori naval forces as the strongest in the country.

The Kuki Suigun that Supported Oda and Toyotomi

Based in Kuki, Owase City, Mie Prefecture, the Kuki Suigun were active primarily in Ise and Shima provinces.
As he expanded his power, Oda Nobunaga made a vassal of Kuki Yoshitaka, who was from the Kuki clan of Shima province.
He then organized a naval force with the Kuki Suigun as its core.
The Oda naval forces led by Yoshitaka played an active role in the subjugation of the Nagashima Ikkō-ikki rebellion and the Ishiyama campaign.

• The Impact of the Tekkosen and the Second Battle of Kizugawaguchi (1578)
  Having been soundly defeated in the First Battle of Kizugawaguchi, Oda Nobunaga ordered Kuki Yoshitaka to build the Tekkosen (iron-clad ships).
  These innovative warships were completely immune to attacks from the Mori naval forces, and instead, they attacked with cannons and firearms, securing victory for the Oda naval forces in just four hours.
  This victory allowed the Oda clan to seize control of Osaka Bay and corner Ishiyama Hongan-ji.
  After Nobunaga’s death, the Kuki Suigun was inherited by Toyotomi Hideyoshi and supported his subsequent efforts to unify Japan.

Other Major Suigun Forces

When Toyotomi Hideyoshi took control of Awaji and Shikoku, he had his retainers, such as Sengoku Hidehisa, Konishi Yukinaga, Kato Yoshiaki, and Wakizaka Yasuharu, form naval forces that participated in the Kyushu and Odawara campaigns.
There were also diverse naval forces in various parts of Japan, such as the Kumano Suigun, which had been involved in the Genpei War since ancient times; the Saika Suigun, famous as a group of musket mercenaries; and the Shiwaku Suigun, which cooperated with and sometimes confronted the Murakami Suigun.
In particular, the Shiwaku-shu, based in the Shiwaku Islands of the Seto Inland Sea, possessed advanced navigation skills.
During the Edo period, they were protected by the Shogunate with a special status called Ninmyo and served as sailors on the Kanrin Maru at the end of the Edo period.

The Role and Fierce Battles of the Suigun in the Korean Invasions (1592–)

The Toyotomi regime’s naval forces were extensively deployed in the invasions of Korea (Bunroku-Keicho no Eki), which began in 1592, and fought fierce battles against the Korean navy.
The Japanese strategy was a “land-sea coordinated strategy,” in which the naval forces would sail north to the southern and western seas to support the advancing land forces, procure war materials, and cooperate in attacks.
However, although the Korean navy was initially devastated, naval commander Yi Sun-sin, leading a fleet that included the Geobukseon (turtle ship) said to have been built under his command, counterattacked and inflicted heavy damage on the Japanese forces.

These battles clearly demonstrate that naval superiority could be a decisive factor in major land operations.
In the Battle of Miyajima, the intervention of the Murakami Suigun decided the victory for the Mori clan, and in the First Battle of Kizugawaguchi, the overwhelming power of the Mori naval forces temporarily defeated the Oda army.
Furthermore, the introduction of the Tekkosen by the Kuki Suigun revolutionized naval warfare, proving that technological innovation could significantly turn the tide of battle.
The importance of the land-sea coordinated strategy in the Korean invasions and the effectiveness of Yi Sun-sin’s turtle ships show that securing maritime supply lines and having innovative warships had a powerful impact on the success or failure of an expedition.
This highlights the strategic reality of the Sengoku period in Japan: those who controlled the sea controlled the nation.

Here is a summary of the major naval forces, their bases, characteristics, and key battles they were involved in.

Major Naval Forces and Their Bases and Characteristics

Main Battles Involving the Suigun

The Disbandment of the Suigun and the Fate of Their Members

The end of the Sengoku period and the progress of national unification drastically changed the fate of the Suigun.
The establishment of a centralized state system would not tolerate the existence of independent armed groups.

Toyotomi Hideyoshi’s “Pirate Suppression Edict”: The Turning Point (1588)

In 1588 (Tensho 16), Toyotomi Hideyoshi issued the Kaizoku Senkin-rei (Edict to Prohibit Piracy).
This law strictly banned activities that had been a crucial source of income for pirate groups, such as collecting tolls at sea checkpoints and engaging in unauthorized foreign trade.
This marked a key turning point, as the Suigun lost the ability to operate as independent forces, eventually disappearing completely within the broader historical trend of centralizing power (military, police, and tax collection) from the medieval to the early modern period.
Following this order, the Noshima clan of the Murakami Suigun became vassals of the Mori clan and commanded the Mori naval forces, while the Kurushima clan, who submitted directly to Hideyoshi, were made daimyo directly under his command and were ordered to maintain a naval force for the Toyotomi clan.
This illustrates the process by which they were integrated from independent maritime forces into a larger power structure.

The Tokugawa Shogunate’s “Large Ship Construction Ban” and the Inland Relocation of Naval Daimyo

The Tokugawa clan, which replaced the Toyotomi clan, further intensified the stabilization and centralization of the country.
The Tokugawa Shogunate issued the Oobune Kenzou Kinrei (Edict to Prohibit the Construction of Large Ships), which forbade daimyo from building military vessels larger than 500 koku.
This temporarily halted Japan’s shipbuilding technology (later, ships for transporting goods, such as the sengokubune, were permitted).
Furthermore, the Shogunate pursued a policy of systematically relocating daimyo who led naval forces to inland territories, severing their connection to maritime affairs.
For example, the Kurushima clan was moved to Bungo Mori, and the Kuki clan to Settsu Sanda.
Kuki Yoshitaka’s fate was tragic: in the Battle of Sekigahara, he sided with the Western Army while his son, Moritaka, sided with the Eastern Army.
After the defeat of the Western Army, Yoshitaka was forced to commit seppuku, bringing the history of the Kuki Suigun to a close.

These policies demonstrate that the decline and disbandment of the Suigun were a historical inevitability resulting from the formation of a centralized state and the establishment of state control over the seas.
Hideyoshi’s edict deprived the Suigun of their economic foundation and autonomy, while the Tokugawa Shogunate’s large ship ban and inland relocations systematically dismantled their military power and severed their ties to the sea, thereby establishing the Shogunate as the sole maritime authority.

The Suigun in Peacetime: Their Role as Funate-gumi

Tokugawa Ieyasu himself had organized the Tokugawa Suigun by inheriting the naval forces of the Imagawa and Takeda clans when he controlled five provinces.
After his relocation to Edo, these forces became the naval forces of the Edo Shogunate.
The Shogunate’s naval bases were established in Uraga on the Miura Peninsula and Nihonbashi in Edo.
They possessed large ships, including the shogun’s personal vessel, the Atakemaru, built in 1631.
However, with the stabilization of the country, the Shogunate’s fleet was reduced, and the aging Atakemaru was dismantled, leading to the disappearance of a full-fledged naval force from Japan.

During the Edo period, the Shogunate and daimyo with coastal territories maintained naval forces known as Funate-gumi, Funate-gata, or Funate-shu.
The descendants of the former pirate groups inherited these positions, but in a long-peaceful era, their roles were limited to managing maritime traffic, inspecting territories, and providing ships for daimyo travel during sankin-kotai (alternate attendance).
The history of the Mukai Suigun also came to an end in 1863, when Katsu Kaishu, a naval commissioner, began to organize a new, modern naval force with sailors under his command 9.

Continuing the Tradition: The Shiwaku-shu and the Dawn of a Modern Navy

However, even as the Suigun were being dismantled, the specialized skills and knowledge they had cultivated were not completely lost.
The Shiwaku-shu from the Shiwaku Islands in the Seto Inland Sea were granted a special status called “Ninmyo” and were protected by the Shogunate, which recognized their self-governance without allegiance to any particular daimyo.
They possessed advanced navigational skills, and this expertise was passed down and used by sailors on the Kanrin Maru at the end of the Edo period.

As Japan entered the final years of the Shogunate, the term “Kaigun” (navy) was already in use, and the name “Suigun” became a thing of the past as the Shogunate and powerful domains began to establish modern fleets modeled after Western nations.
However, many sailors with a naval tradition, including those from the Shiwaku Islands, became the early pioneers of the modern navy at the end of the Edo period.
This shows that even after the Suigun were disbanded as a military organization, the specialized human capital they had cultivated contributed to Japan’s modernization in a new form.
Their navigational skills and knowledge of the sea became the foundation for building a new national naval power.

Conclusion: The Legacy and Modern Influence of Japan’s Suigun

Japan’s Suigun were far more than just a group of sea bandits; they were a complex and multi-faceted group of maritime professionals.
Their activities originated with ancient sea people, and they evolved into Keigo-shu (guard groups) that maintained order in maritime traffic in the medieval period, and then into the Suigun – a critical military and economic force for daimyo in the Sengoku period.
They managed maritime traffic, conducted their own economic activities, and wielded decisive power that could sway the course of land battles.

However, their independence and military strength were gradually lost due to centralizing policies like Toyotomi Hideyoshi’s “Pirate Suppression Edict” and the Tokugawa Shogunate’s “Large Ship Construction Ban.”
They eventually faded away with the arrival of a peaceful era.
This was a historical inevitability, as autonomous maritime forces had to cede their roles as the state established a monopoly on military power and comprehensive national governance, including over the seas.

Still, the advanced navigational skills, knowledge of the sea, and the spirit of survival at sea that they had cultivated over centuries were not completely lost.
They took on a new form as Funate-gumi (naval units) during the Edo period and were later inherited by the sailors of the Kanrin Maru at the dawn of the modern navy, contributing to Japan’s modernization.
Their existence demonstrates that even when old systems are dismantled, the specialized human capital nurtured within them can become the foundation for new national capabilities in a new era.

As modern stories like “One Piece” use pirates as a motif, the history of Japan’s Suigun offers us many insights as a profound story of real-life maritime romance, strategy, and daily life that transcends mere fiction.
Their existence reminds us that the sea has always been an indispensable element in Japanese history and culture.

References

• SHIMANAMI PEOPLE: What is the difference between a navy and a pirate?
• HomeMate: Battle of Kizugawaguchi
• Akira Ishikawa, former reporter for the Tohto Yomiuri Shimbun: Learning from Mukai Masanori
• Wikipedia: SUIGUN

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