Hwacha

The hwacha or hwach'a was a multiple rocket launcher and an organ gun of similar design which were developed in fifteenth century Korea. The former variant fired one or two hundred rocket-powered arrows while the latter fired several dozen iron-headed arrows or bolts out of gun barrels. The term was used to refer to other war wagons or other cart-based artillery in later periods, such as that developed by Byeon Yijung in the 1590s.

These weapons were notably deployed in the defense of the Korean Peninsula against the invading Japanese when they invaded in the 1590s. Some East Asian historians believe this technological breakthrough, alongside the turtle ship in the mid-16th century, had a distinctive effect during the war.

Hwachas appear in Korean museums, national parks, and popular culture today.

Early firearms
Firearms were recognized by Goryeo military leaders as necessary for national defense. Constituting a particular threat was Japanese raiders, who frequently plundered coastal towns in increasing numbers from 1350 onward. Gunpowder and firearms explicitly for combating them on the sea were imported from China in 1374 but the necessary expertise for production was still restricted by Chinese government policy.

Numerous ancient Chinese documents relating to gunpowder based weapons such as the Huolongjing were acquired by the Koreans in addition to small samples of Chinese gunpowder which the Koreans reverse engineered.

Local production did not begin until Ch'oe Mu-sŏn, having acquired the methods for purifying potassium nitrate from visiting Chinese merchants, accomplished it between 1374 and 1376. A government office for developing gunpowder and firearms was established in 1377, with Ch'oe appointed its head. Several weapons were developed here, including hand-cannon and a series of rockets, in particular the juhwa.

Hwacha
The hwacha further developed from the juhwa and the singijeon. The first hwacha was created in Korea in 1409 during the Joseon Dynasty by several Korean scientists, including Yi To (, not to be mistaken for Sejong the Great, due to the similarity in their names) and Ch'oe Hae-san, son of Ch'oe Mu-sŏn). Stronger and more effective hwachas were made in 1451 under the decree of King Munjong, by the king himself and his younger brother Pe. Im-Yung (Yi Gu, ). The Munjong Hwacha is a well-known type that could fire 100 rocket arrows or could be used as a Volley gun type weapon capable of firing 200 darts with 50 Chongtong at one time with changeable modules. At the time, 50 units were deployed in Hanseong (present-day Seoul) and another 80 on the northern border. By the end of 1451, hundreds of hwachas were deployed throughout the peninsula. Another variant was the Mangam Hwacha. A boxed cart with large faces of a dokkaebi painted on all three sides. Armed with forty seungja-chongtongs with fourteen in the front and thirteen on the left and right sides, it required two soldiers to operate, one firing and the other reloading. This weapon was capable of firing 600 bullets, with each barrel holding 15 shots.

Imjin wars (1592–1598)
Hwachas saw action most extensively against the Japanese during their invasions of Korea. The hwachas were primarily placed in fortresses or citadels, and used defensively. They proved decisive in many battles and were most prominent in the Battle of Haengju, in which 3,400 Koreans repelled 30,000 Japanese with the help of 40 hwachas. The Japanese samurai infantry, especially in the Battle of Haengju, typically advanced in dense formations, presenting ideal targets for the hwacha.

Hwachas were also used on panokseons under the navy of Admiral Yi Sun-sin to attack Japanese ships from a distance.

Components
The hwacha's structure was very similar to a handcart. Its top contained a mobile wooden launchpad containing 100 to 200 cylindrical holes, into which igniters like those of the sajeonchongtong were placed.

The ammunition, similar to the ancient Chinese fire arrows, consisted of a 1.1 m long arrow with the addition of a gunpowder-filled paper tube attached to the shaft just below the head. Approximately 100 projectiles were loaded and launched in one volley, and had a range of up to 2,000 m.

One variant had 5 rows of 10 gun barrels in the launchpad, each of which could fire a bundle of four arrow-like projectiles.

The back side of the hwacha featured two parallel arms that allowed the operator to push and pull the machine and a vertical strip designed for in-line attacks or ground-sentry positions.

Wood pivots and iron axles usually fastened the wagon-like wheels. To reduce friction between the wheels and the axles, tar oil was used.

Hwachas were usually made of pine wood, although some were made of oak. The ropes used were typically made of hemp.

The Korean army included siege engineers and blacksmiths to repair the hwacha in case of damage due to poor road conditions, bad weather, or battle.

Projectiles
Unlike the cannons or mortars used in Western warfare during Middle Ages and the 16th century, which required heavy iron balls, hwachas fired arrows which were thin and light, making it an easy-to-maneuver siege weapon.

The holes in the hwacha's launching array ranged in diameter from 2.5-4 cm, which allowed thin Gungdo bow-like arrows to be fired and also admitted sajeonchongtong class igniters placed in the back side of the shooting board.

Singijeon-class projectiles were small arrows designed by Korean siege engineers specifically for hwachas use. Called so, or "small", they possessed a pouch of black powder attached in the bottom near to the fletching section. Besides the singijeon-class projectiles, hwacha could fire 100 steel-tipped rockets.

Because of the large numbers of arrows fired from hwachas and the widespread damage caused by its attack, a dense formation presented an ideal target for hwachas.

Ballistics and range
The trajectory of the so projectiles was relatively flat and – like other spinning projectiles – affected by the Magnus effect. Operators used to fire the weapon at an elevation of nearly 45° to maximize range. Adverse weather conditions (wind, humidity, rain) during a battle generally limited their striking distance to about 100 m.

Hwachas' range could be extended if the siege weapon was situated on a hill or other elevated place. Singijeon arrows from that position had a range of about 500 yd.

A 15th-century account from the Annals of Joseon Dynasty tells of an experiment in which the singijeon fired from a hwacha completely pierced a scarecrow armed with a suit of armor and shield, at the range of 80 paces (about 100 m).

Usage


Hwachas were mostly used defensively; however, some Western and East Asian historians have concluded that in some cases, they were used offensively in sea-to-land attacks and in naval warfare as well, particularly in the Battle of Noryang Point, during the Imjin wars in 1598.

Hwachas were usually carried to battle and highly escorted. Once the army had settled down in trenches or base camps, the operators would assemble the siege weapon by unpacking the launching array and placing it on top of the wooden frame of the cart. In this regard, the Hwacha is similar to the European trebuchet, which also was transported in parts to be assembled on the battlefield before use.

Once a hwacha was set up for combat, the operators would use the gunpowder stored in a boot-like bag tied on each igniter to be used for each hole on the machine. Afterward, the operators could load the hwacha with arrows or iron spikes and be ready to shoot. To do so, they stepped back, covered their ears, and pulled the rope for each igniter.

At sea, maneuvers were slightly different and more complex because the operator would need to find a proper and stable place to fire. Some hwacha operators preferred to be on the rowers' deck, where they could shoot from the windows, while others preferred to be on the main deck to shoot at the enemy ships' sails. These kind of manoeuvres were particularly seen on Korean Panokseon warships.