A hwacha is a multiple rocket launcher from the 15th century, and also a symbol of ingenuity and resourcefulness and, optionally, Korean independance. It looks like this:

Executive Summary

When were they made?

Hwachas were made throughout the 15th and 16th centuries in Korea.

Of course, there is a lot to say about the history of the hwacha and about the degree to which it can be considered a Korean invention.

Why were they made?

Hwachas were made at first to keep Japanese pirates away, and later to keep the entire Japanese army away.

Of course, there is a lot to say about what exactly constitutes 'Japanese' and 'Korean' at various points in north-east Asian history, but it doesn't belong in this article.

How were they made?

Wood, iron, gunpowder, and a willingness to experiment!

Of course, there's a lot to say about the struggle to obtain the gunpowder.

When were they used?

Most famously, hwachas were used during the Imjin War, Toyotomi Hideyoshi's invasion of Korea.

Of course, there's a lot to say about the battle of Haengju, the most famous hwacha battle in history.

How effective were they?

Well, they certainly had a strong effect on anyone standing in front of them.

Of course, there's a lot to say about the exact effectiveness of these wonderful devices.

What is their place in history?

Forgotten until recently, but now you can hardly move for hwachas -- at least if you're in a Korean war memorial or historical drama.

As ever, there's a lot to say about hwachas today. Shortly after the era of the hwacha, Korea fell under the control of first Ming China, then the Manchus, and then Japan, and the memory of this

History

Hwachas were first constructed in 1407, as part of King Sejong the Great's programme of military buildup:

• 1377: Gunpowder is first mass-produced domestically in Korea (see below)
• Late 1300s: Early 'juhwa' rockets, based on Chinese 'fire arrows', are produced in Korea
• Later 1300s: Smaller 'singijeon' fire arrows are developed
• 1409: Multiple rocket launcher, i.e. a hwacha, is demonstrated to King Sejong the Great
• 1409-1450: King Sejong constructs about 90 hwacha, but it's unclear whether they participated in his campaigns against Tsushima and Manchuria
• 1451: King Munjeon's administration begins producing hwacha in bulk and they become an integral part of border defences

Some hundreds of hwacha existed throughout Korea by the time of the Imjin War (1593). During the reigns of Sejong and Munjeon, there was considerable interest in technological solutions to the problem of security, and in gunpowder weapons in particular. This interest was to die away later in the Joseon period -- notably, the Japanese troops in the Imjin War were plentifully supplied with arquebuses whereas Korea's firearms were still limited to those invented during the 15th century.

As a result, even though the hwacha's deployment spans 200 years, almost all change and development took place during the earlier part of that time.

The first hwachas fired 100 of the small-sized 'singijeon' rockets; King Munjeon's hwachas fired 200 and by that time further grades of ammunition had been added, requiring different launching devices. Whereas 'singijeon' were simply stuck through the holes in the hwacha's launch board, heavier ammunition was launched from tiny cannon, called 'sajunchongtong', which served both to ignite the propellant and to shoot the missile out of the launch board.

To accommodate this difference, the hwacha was made using seperate, interchangeable components, with the chassis having pegs into which different styles of launcher could be fitted -- it may also be that the sajunchongtong were replaceable within the board, since they would have been more valuable than the wooden frame around them. This made the hwacha far ahead of its time in terms of modularity and maintainability.

The Quest for Gunpowder

The history of the hwacha is inextricably linked with that of Choi Mu-Seon ('choi' is pronounced 'che' due to some smoothing-down of Korean phonetics since King Sejong's time).

Born in the last years of the Goryeo period, Mu-Seon struggled for many years to find a way to repel the Japanese raiders who ravaged Korea (given that the Goryeo administration and local Korean populations were ineffective). He introduced gunpowder weapons from China, but Yuan China was understandably reluctant to supply large quantities of gunpowder.

Embarking on a long search, Choi Mu-Seon discovered the formula for gunpowder but had no effective way of obtaining nitrates. He did, however, succeed in impressing his own and succeeding generations with his scientific approach and in gathering great political support, and eventually in bribing a Chinese merchant to reveal the method of extracting potassium nitrate from the soil.

Armed with these successes, Choi Mu-Seon managed to create a naval fire weapon which he saw used at the battle of Jinpo in 1380, destroying hundreds of Japanese ships and ensuring that the new Joseon kingdom of Korea would look to gunpowder as the future of defence.

Choi Mu-Seon went down in history as the very archetype of a scientist and scholar, which seems to teach us the sad lesson that technological success depends on investment and publicity as much as on research.

Capabilities

By modern standards, neither Choi Mu-Seon's creations nor the hwacha of the Imjin War period would have seemed very effective. Accuracy and range were both appalling; the smallest singijeong arrows (arrows with a tube of gunpowder attached to them) are thought to have had a range of about 100-150 yards. Larger rockets would have gone further -- the juhwa rocket, too large to be fired from a hwacha, would probably have travelled almost a mile. Stabilization was by means of fins (as used for cannon projectiles at the time).

The fact that the hwacha appears to have been fired with the trails at the back lifted up, to point the rockets dead forward, suggests that they weren't accurate enough to be fired upward for range but were instead fired straight at a relatively nearby enemy.

Larger missiles having an explosive warhead were used, and it appears that gunners tried to time the missile to explode roughly on top of enemy, by varying the length of the gunpowder propellant tube. This is a rather advanced feature -- perhaps the short range and flat trajectory made the calculation easy, or perhaps the hwacha could actually be used in a 'bombardment' mode on an arcing trajectory.

Certainly, the hwacha was most effective against large, slow targets such as dense blocks of infantry and ships. We do not hear of it being used against fortifications or on the open battlefield.

Comparison with Chinese equivalents

China had produced wheeled multiple rocket launchers during the 14th century. These had some things in common with the hwacha:

• Different launchers could be fitted to a standard chassis
• All rockets could be launched at once

However there were also many differences, so much so that it's not obvious that the Chinese devices directly inspired the hwacha:

• Chinese launchers generally had blades and spikes
• Chinese launchers often had protection for the gunners
• Chinese launchers often had single wheels, meaning that they were fired on the move

The general design of Chinese launchers seems to suggest that they were used at very close range and in an offensive role, charging an enemy formation and being detonated right in their faces. Such a role would be a good match for Ming Chinese tactical doctrine, which emphasised a massive downhill rush of footsoldiers. In this, Ming rocket launchers are very different from the longer-range, defensive hwacha.

The Battle of Haengju

In 1503, famously, a Japanese force of 30,000 attacked the fortress of Haengju (행주) and it's defenders, and were largely wiped out.

As a Joseon-era border fort, Haengju had a complement of 40 hwacha which in this case were emplaced in the perimeter wall. These were used in the defence, although mortars, pikes, rocks, stakes, trees, and probably every throwable object were also used. The defenders numbered between 2,800 and 3,400, while the number of attackers is said to have declined by fully 10,000 men during the course of the battle.

Despite nine assaults, the fortress stood, and a serious blow was dealt to Toyotomi Hideyoshi's invasion of Korea. The Korean commander, Gwon Yul, attributed victory to the fortress' hwachas!

In military terms, the battle of Haengju was just one in the dreary succession of one-sided, doomed uphill assaults with which history is marked. It's much more interesting for the personalities of the opposing commanders -- the stern, severe patriot Gwon Yul (권율) and the Spartan, violent, power-hungry samurai Kato Kiyomasa (加藤清正).

Hwachas Today

Rather like the even more famous kabokseon, the ironclad 'turtle ship' of the Imjin War era, the hwacha no longer forms part of Korea's arsenal. The age of the Imjin War was followed rapidly by Chinese domination of Korea, followed by Manchu domination, followed by Japanese domination, circumstances which tended to suppress the memory of Korean achievements in this area.

In recent decades, the kabokseon has become something of an icon (and, ingenious though it was, it's role has perhaps come to be a little overstated). This has happened with the hwacha only to a lesser degree -- there have been some reconstructions made and it's a perennial favorite with strategy games that need a Korean unit, but it's not really as photogenic as the turtle ship.

Much of our modern knowledge of the actual shape of the hwacha comes from a single book, the 'gukjo-o-ryeui' 국조오례의 (in hanja, 國朝五禮儀) of 1474. This standard court record contains a long section on gunpowder ordnance including a very detailed woodblock print of a hwacha.