text: Korea had already come into possession of cannons by 1373, when a Korean mission was sent to China requesting gunpowder supplies for the artillery on their ships. However Korea did not natively produce gunpowder until the years 1374–76. In the 14th century a Korean scholar named Choe Museon discovered a way to produce it after visiting China and bribing a merchant by the name of Li Yuan for the gunpowder formula. In 1377 he figured out how to extract potassium nitrate from the soil and subsequently invented the juhwa, Korea's first rocket, and further developments led to the birth of singijeons, Korean arrow rockets. Korea also began producing cannons in 1377. The multiple rocket launcher known as hwacha ("fire cart" 火車) was developed from the juhwa and singijeon in Korea by 1409 during the Joseon Dynasty. Its inventors include Yi Do (이도, not to be mistaken for Sejong the Great) and Choi Hae-san (최해산, son of Choe Museon). However the first hwachas did not fire rockets, but used mounted bronze guns that shot iron-fletched darts. Rocket launching hwachas were developed in 1451 under the decree of King Munjong and his younger brother Pe. ImYung (Yi Gu, 임영대군 이구). This "Munjong Hwacha" is the well-known type today, and could fire 100 rocket arrows or 200 small Chongtong bullets 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 Korea.
  Naval gunpowder weapons also appeared and were rapidly adopted by Korean ships for conflicts against Japanese pirates in 1380 and 1383. By 1410, 160 Korean ships were reported to have equipped artillery of some sort. Mortars firing thunder-crash bombs are known to have been used, and four types of cannons are mentioned: chonja (heaven), chija (earth), hyonja (black), and hwangja (yellow), but their specifications are unknown. These cannons typically shot wooden arrows tipped with iron, the longest of which were nine feet long, but stone and iron balls were sometimes used as well.