The Limited Role of Naval Artillery in Japanese Warfare

Compared to the abundant records of boarding actions, documented instances of Japanese warships engaging in artillery duels are remarkably scarce. The most notable examples did not occur in ship-to-ship combat but rather in naval bombardments supporting land operations. Japan’s first recorded coastal bombardment took place during the 1561 siege of Moji Castle, though ironically, the cannon fire came from Portuguese vessels whose captains assumed significant political risks by participating. This pattern continued in the 1584 Battle of Okitanawate, where Shimazu forces employed large-caliber shipboard guns (likely breech-loading Portuguese-style “Frankish cannons”) to support infantry movements along the beach, with gunners reportedly praying as they reloaded.

The Technological Limitations of Japanese Naval Armament

Throughout most of the samurai era, Japan lacked true naval artillery. The heaviest weapons available for shipboard use remained these imported Frankish cannons until European vessels began frequenting Japanese ports. Particularly after the Battle of Sekigahara, the cannons aboard European merchant ships became more valuable than their cargo. However, none of these acquired European guns were ever reinstalled on Japanese vessels. Instead, they were repurposed as siege weapons – the structural limitations of atakebune (Japanese warships) made them incapable of withstanding the recoil forces generated by European artillery.

This technological gap explains why references to Oda Nobunaga’s fleet using “great guns” during the 1573-74 sieges of Nagashima’s Ikko-ikki fortresses should be understood as large-caliber arquebuses rather than European-style naval artillery. Similarly, when Korean Admiral Yi Sun-sin lamented losing his “Cheon” and “Hyeon” class cannons to Japanese fire, he referred to coastal batteries rather than ship-mounted weapons. True ship-to-shore bombardment wouldn’t occur until the 1614 Siege of Osaka.

An Unconventional Coastal Defense: Elephant Artillery

One of Asia’s most peculiar coastal engagements occurred in 1633 near the Siamese coast. Following the murder of Japanese adventurer Yamada Nagamasa in Siam, Siamese forces attacked Japanese settlements and imprisoned eight samurai. When Javanese pirates (possibly a generic term for Southeast Asian raiders) attacked Siam, the king – recognizing Japan’s fearsome reputation – offered the prisoners freedom in exchange for military assistance.

The samurai devised an ingenious defense: they armed seventy Siamese soldiers with Japanese armor to create the illusion of a larger Japanese force and mounted two small cannons on each of eight elephants. Chronicles describe how this improvised “coastal artillery corps” successfully repelled the pirate fleet: “They began fierce bombardment as soon as Javanese ships appeared…had the enemy not prudently retreated, they could have sunk the entire Javanese fleet.”

Incendiary and Rocket Weapons in Naval Combat

During the Sengoku period, Japanese warships employed various incendiary weapons alongside conventional archery. These included:
– Rockets launched from standard bows
– Larger Korean-style wooden arrows with iron heads (convertible to rockets) fired from cannons
– Spherical bombs called “horokubiya” (pot-style rockets)
– Various incendiary devices structurally similar to Chinese models, constructed from iron, ceramic, or thick cardboard

One particularly innovative design could be swung on a rope before release, while others were launched using netted poles resembling lacrosse sticks or traction trebuchets. These weapons proved devastating in ship-to-ship combat, with records indicating Oda Nobunaga’s general Sakuma Nobushige had his flagship set ablaze by a Mori-launched incendiary device.

Tactical Formations and Naval Doctrine

Japanese naval tactics mirrored land warfare principles, with the commanding general maintaining a central position in the formation. The typical battle fleet comprised:
– Atakebune: Heavily armed command ships
– Sekibune: Medium warships
– Kobaya: Small, fast vessels for communication

Standard naval formations included:
1. Tsuruyoku (Crane Wing): An offensive formation with concave center and advanced flanks
2. Hoen (Protective Circle): A defensive anchored formation with ships encircling the flagship
3. Ganko (Stubborn): Ships advancing at angles to the main axis
4. Gyorin (Fish Scales): Defensive formation with all ships forward, easily convertible to attack

The Pinnacle of Classical Naval Warfare: Dan-no-ura (1185)

The 1185 Battle of Dan-no-ura stands as Japan’s most decisive naval engagement, showcasing sophisticated tactics and the critical role of environmental factors. The Genji fleet formed a linear formation bow-to-stern, while the Heike deployed three squadrons. Initial long-range archery exchanges favored the Heike, whose commander Taira no Tomomori expertly utilized tidal currents to attempt an encirclement.

The turning point came when tides shifted westward through the strait, granting the Genji fleet superior maneuverability. This advantage, combined with the betrayal of Miura Yoshizumi (who revealed the location of the child Emperor Antoku), allowed the Genji to concentrate fire on enemy oarsmen and helmsmen. As Heike ships lost control and drifted, mass suicides followed, including the deliberate drowning of the young emperor to prevent capture.

Combined Operations: Army-Navy Coordination

Japanese military tradition valued combined arms operations, with two notable examples:

1. 1281 Mongol Invasions: Japanese “small boat” tactics against the Mongol fleet became legendary. Nighttime boarding actions using lowered masts as bridges, daytime swimming assaults (including one where 30 samurai swam to a Mongol ship, beheaded the crew, and swam back), and fire attacks demonstrated remarkable ingenuity. Mongol countermeasures included chaining ships together and using traction trebuchets, but the tactics proved effective until the kamikaze (divine wind) completed Japan’s defense.

2. 1555 Battle of Miyajima: The Mori clan’s amphibious operation against Sue Harukata represents a masterpiece of deception. After luring Sue’s forces onto Miyajima Island, Mori Motonari executed a coordinated pincer movement – his son Kobayakawa Takakage feinted along the strait while the main force landed at night during a storm to attack from the rear at dawn.

The Legacy of Japan’s Naval Heritage

Japan’s naval evolution reflects broader patterns in military technological diffusion and adaptation. The reliance on boarding actions and coastal artillery rather than ship-to-ship gunnery duels highlights both technological limitations and the dominance of samurai close-combat ethos. The ingenious improvised solutions – from elephant artillery to nighttime boarding raids – demonstrate remarkable tactical flexibility that would later characterize Japan’s rapid naval modernization in the 19th century. These historical precedents of combined operations and emphasis on deception and surprise remain embedded in Japanese military doctrine to this day.