How the Panokseon Became the True Workhorse of the Imjin War

From Maengseon to Panokseon: The Evolution of Joseon Warships

1. Why Joseon Had to Start by Rebuilding Its Ships

In the early Joseon period, the basic naval platform was the maengseon (“fierce ship”).
Under King Sejo, official military transport ships (byeongjoseon) were standardized as dual-use vessels for both warfare and grain transport, and by the time of the Gyeongguk Daejeon legal code they appear as large, medium, and small maengseon as the standard warships.

That compromise came with serious problems:

Because they also had to carry tribute grain, they were heavy and sluggish.
In peacetime they were logistics workhorses; in wartime they were expected to double as combat ships, which meant they were far from optimized for battle.
From the 16th century, with armed Japanese traders and coastal raiders becoming more dangerous, maengseon were increasingly criticized for lacking both agility and firepower.(위키백과)

Court records from the Seongjong and Jungjong eras already complain that maengseon are too heavy and slow, and various officials propose increasing the number of small, fast craft (so-called “swift ships”). But when fleets shifted toward smaller hulls, another problem appeared: they died quickly under concentrated enemy fire and boarding attacks.

In short:

“Build them heavy and they can’t move. Build them light and they shatter when hit.”

Joseon’s navy lived inside that dilemma through most of the 16th century.

The answer they eventually arrived at was a purpose-built, two-deck fighting ship: the panokseon.

2. From Sejo’s Military Transports to Myeongjong’s Panokseon

(1) The Roots: Byeongjoseon and Maengseon

To be fair, byeongjoseon and maengseon were not useless relics.
Joseon absolutely needed a secure state grain network along the Yellow Sea and South Sea coasts, so “warship that can also haul rice” was the political compromise baked into early designs. For a while that balance worked.

But by the mid-1500s the environment changed:

Japanese coastal forces were sailing larger, more heavily armed ships.
Fighting was no longer just small raids; larger fleet actions near open water became plausible.
Japanese tactics increasingly relied on closing in, grappling, and boarding after a few volleys of gunfire.(Korea.net)

A heavy, half-freighter maengseon was now too slow, too soft, and too low-sided for this new style of war.

(2) The Turning Point: Eulmyo Waebyun and the Demand for a “Tall, Steep Warship”

The large Japanese raid of 1555 (the Eulmyo Waebyun) triggered a serious rethink.
From then on, memorials to the throne start repeating a common theme:

“We need a tall, steep warship so high that the enemy cannot easily jump aboard.”

In design terms, that meant:

Higher freeboard and upper structure
A weapons deck from which guns and arrows could fire downward
Oarsmen protected underneath, instead of being exposed along the sides

The ship that embodied these demands was a big, flat-bottomed, two-deck warship: the panokseon (literally “planked house ship,” from the enclosed upper structure).(위키백과)

3. What Did a Panokseon Actually Look Like?

(1) Flat Bottom, No Keel

The panokseon was a classic Korean coastal warship, part of the broader hanseon tradition. Its key structural traits:

Flat bottom (pyeongjeo) for stability in shallow coastal waters
No Western-style central keel; instead, a wide bottom plank and side planking
Transverse beams tying the sides together in a box-like hull(위키백과)

That meant:

It excelled in shallow, tidal waters like those of Korea’s west and south coasts.
At low tide it could sit upright on mudflats or be dragged ashore for repair.
It was less suitable for blue-water ocean operations, but Joseon’s navy fought mainly in coastal seas and straits, so this trade-off made sense.

Japanese warships, by contrast, tended to have deeper, V-shaped hulls optimized for different kinds of waters, which could be a disadvantage in Korea’s extreme tidal environments.(Korea.net)

(2) Two Decks: Separation of Muscle and Firepower

The real revolution was the two-deck layout:

Lower deck: rowers and some support personnel
Upper deck (the “panok”): gunners, archers, and melee troops

This gave four big advantages:

Rower protection
Oarsmen were shielded from arrows, matchlock bullets, and splinters, so the ship could survive longer engagement cycles without losing propulsion.
Higher firing position
Guns and archers shooting from a raised deck enjoyed better range and plunging fire angles.
Anti-boarding geometry
Taller sides made it physically harder for Japanese marines to grab the rail and swarm aboard—something Japanese accounts complain about repeatedly during the Imjin War.(Facebook)
Command and visibility
A small “general’s tower” on top of the upper deck gave the commander clear sightlines for flags, drums, and signals.

(3) Size and Crew

Exact dimensions vary by source, but most reconstructions converge around:

Length: roughly 20–30 meters
Beam (width): around 8–10 meters
Complement: on the order of 100 personnel (rowers, gunners, archers, officers, marines)(위키백과)

In modern terms, think of something comparable in footprint to a small modern tug or coastal patrol boat—but built of thick timber, with two decks and loaded with guns.

4. Panokseon vs. Japanese Warships: Different Ships, Different Ideas of War

(1) Japanese Atakebune and the Boarding Paradigm

In the Sengoku and early Imjin War era, Japanese fleets relied on large command ships like the atakebune, supported by medium and small craft.

Their basic concept of naval combat looked like this:

Fire some arrows and matchlock volleys to soften the target
Close the distance and grapple
Send warriors swarming onto the enemy deck for close-quarters fighting with swords and spears(Korea.net)

In that paradigm, the ship is primarily a floating delivery platform for infantry. Firearms are important, but they are the prelude to boarding, not the main way of deciding the battle.

(2) Joseon’s Alternative: Artillery-First, Keep Them Off the Deck

Joseon, by contrast, had a long record of developing gunpowder artillery well before the Imjin War. Under King Sejong and his successors, several families of cannon—cheonja, jija, hyeonja, and hwangja chongtong—were standardized and progressively lightened for naval use.(uexinja.blogspot.com)

Very roughly:

Cheonja (“heaven”) guns: the largest pieces, long range but fewer in number
Jija (“earth”) and hyeonja (“black”) guns: medium calibers, the practical workhorses in battle
Hwangja (“yellow”) and smaller portable pieces: short-range, multi-shot, or grapeshot-type roles; some overlapped the space where we might put hand-cannon today

Some royal chronicles boast extremely long ranges—far over a kilometer—using idealized “paces” and test shots. Modern analysis is more cautious: effective combat ranges of a few hundred meters are more realistic, but that was still enough to outrange typical Japanese small guns and small-caliber boat guns of the time, especially when firing from a high upper deck.(위키백과)

A panokseon’s layout made full use of this doctrine:

Cannons distributed along the bow, stern, and sides so the ship could fire in any direction
Space on the upper deck for mixed volleys of cannon and massed archery
The ability to create “layers” of fire:
- Long and mid-range bombardment with artillery
- Archery as the enemy approached
- Small guns and anti-personnel rounds if a ship got dangerously close

Where Japanese doctrine said, “Shoot, then board,” Joseon’s answer was:

“Shoot so much, from so far, and from so high that they never get the chance to board at all.”

The panokseon’s tall sides and two-deck layout were the physical hardware behind that idea.

5. Imjin War Case Studies: Where the Panokseon Proved Itself (and Where It Didn’t)

(1) Hansan Island: A Textbook Panokseon Battle

The Battle of Hansan Island (1592) is often cited as the panokseon’s masterpiece.

Admiral Yi Sun-sin deployed a panokseon fleet in his famous crane-wing formation, curving around the Japanese fleet.
As the Japanese ships pressed inward, they sailed deeper into overlapping fields of cannon and arrow fire from both “wings.”(Facebook)

In this battle, the famous turtle ships (geobukseon) were shock units used for disruption and breakthrough. The bulk of the destruction was delivered by panokseon squadrons firing in disciplined waves.

(2) Myeongnyang: Ship Design Meets Geography

At Myeongnyang Strait (1597), Admiral Yi faced an overwhelming numerical disadvantage. He compensated with:

Violent tidal currents in a narrow passage
Flat-bottomed, strongly built panokseon that could better ride those currents and pivot quickly
Concentrated fire from upper decks against Japanese ships thrown into chaos by the water(Facebook)

Again, the panokseon was not a magic weapon by itself, but its structural traits matched the environment almost perfectly.

(3) Not an Invincible “Wonder Ship”

It is important not to over-mythologize:

Joseon cannons still faced limitations in powder quality, metallurgy, and aiming; they required extensive training and maintenance.
The panokseon’s flat bottom, while ideal for coastal waters and tidal straits, made it less suitable for the open ocean and heavy swell.
The Japanese navy evolved too, experimenting with heavier guns and modified warships after the shock of early defeats.(Korea.net)

So the panokseon’s superiority was not that “one ship class was absolutely the strongest in the world,” but that:

Its hull form fit Korea’s coastal geography,
Its two-deck layout fit Joseon artillery doctrine, and
It matured inside a navy that had trained with gunpowder weapons for decades.

Those three layers together created the edge we see in the historical record.

6. Blog-Friendly Takeaways: Why the Panokseon Matters

If you want to distill this into a punchy blog conclusion, these are solid anchor points:

Joseon’s naval victories were not lucky accidents.
The panokseon was the result of several decades of thinking about:
- Heavy vs. light hulls
- Transport duties vs. pure combat roles
- How to counter Japanese boarding tactics with artillery and height
The turtle ship was the symbol; the panokseon was the day-to-day firepower.
Turtle ships were few in number and highly specialized.
The panokseon carried most of the fleet’s guns, most of the sailors, and did most of the actual fighting.
“Local design beats imported templates.”
The panokseon’s flat bottom, no-keel box hull, and double-deck structure look alien next to Western sailing ships of the same era.
But for the shallow, tidal, island-strewn seas of Korea—and for a doctrine built around artillery rather than heroic boarding parties—it was exactly the right tool.

If you frame it that way, your article naturally shifts from:

“We had a cool ship once”

to:

“Here is how a small country, stuck between powerful neighbors, used ship design, geography, and doctrine to punch far above its weight at sea.”

And in that story, the quiet MVP is not the spiky turtle ship on the movie poster,
but the panokseon, the real workhorse of the Imjin War.

A light history story

Thursday, November 20, 2025

The Real Ace Behind the Turtle Ship: Panokseon