Righteous armies
Righteous armies (Korean: 의병), sometimes translated as irregular armies or militias, were informal civilian militias that appeared several times in Korean history, when the national armies were in need of assistance. The first righteous armies emerged during the Khitan invasions of Korea and the Mongol invasions of Korea. They subsequently rose up during the Japanese invasions of Korea (1592–1598), the first and second Manchu invasions, and during the Japanese occupation and preceding events. During the long period of Japanese intervention and annexation from 1890 to 1945, the disbanded imperial guard, and Confucian scholars, as well as farmers, formed over 60 successive righteous armies to fight for Korean freedom on the Korean peninsula. These were preceded by the Donghak movement, and succeeded by various Korean independence movements in the 1920s and beyond, which declared Korean independence from Japanese occupation.
Righteous armies (Korean: 의병), sometimes translated as irregular armies or militias, were informal civilian militias that appeared several times in Korean history, when the national armies were in need of assistance.
The first righteous armies emerged during the Khitan invasions of Korea and the Mongol invasions of Korea. They subsequently rose up during the Japanese invasions of Korea (1592–1598), the first and second Manchu invasions, and during the Japanese occupation and preceding events.
During the long period of Japanese intervention and annexation from 1890 to 1945, the disbanded imperial guard, and Confucian scholars, as well as farmers, formed over 60 successive righteous armies to fight for Korean freedom on the Korean peninsula. These were preceded by the Donghak movement, and succeeded by various Korean independence movements in the 1920s and beyond, which declared Korean independence from Japanese occupation.

During the Japanese invasions under Hideyoshi of Korea
The righteous armies were an irregular military that fought the Japanese army that twice invaded Korea during the Japanese invasions of Korea (1592–1598). Righteous armies were most active in the Jeolla Province in the southwestern area of Korea. Righteous armies included peasants, scholars, former government officials, as well as Buddhist warrior monks. Righteous armies were important during the war because a significant portion of the expected government organized resistance had been destroyed in Gyeongsang and Chungcheong Provinces in the south by the force of Japanese arms at the outset.  The natural defenders had been stripped away and the residue had been called north to help protect the fleeing king.  Moreover, many of the district officers had obtained their commissions not through merit, but by bribery or influence, and were essentially incompetent or cowards.  This was highlighted in their performance and in the performance of their units in the early days of the conflict.
This kind of resistance was totally unexpected by the Japanese invaders. In Japanese warfare, when the leaders fall, civilians would simply submit. However, upon learning that the Korean people were forming organized resistance against them, the Japanese were shocked. Japanese strategies were based on the premise that the people of Korea would submit to them and assist their supply line by giving their food. However, this was not the case and righteous armies continued to interrupt the Japanese supply line. People's voluntary resistance movements were one of the major reasons why Japanese invasion was not successful.
Righteous army was organized and led by seonbi, who was Confucian philospher and mostly trained archers. Political positions, social status, and economic interests were not consistent between the righteous army commander who created the righteous army during the Japanese Invasion of Korea in 1592, but there was a factor that made them combine.
First, most of the righteous army chiefs were former civil servants among the aristocrats, but most of them were former officials. The spirit of Geunwang spread among local Confucian scholars in order to practice Confucian Taoism, which was usually learned as a local giant, and they were enraged by the incompetence and cowardice of the local leader and armed men.
Second, the creativity of the righteous army was for the defense of the local people and their relatives, and furthermore, it was the manifestation of national sentiment for Japan's barbarity. Joseon, which regarded Confucian ethics as a thorough social norm, considered the Japanese as aggressors because of the continuous looting of Japanese pirates from the end of Goryeo, and culturally despised them and called them Wae or Seom Orang-ke. When invaded by Japan, it was the creativity of the righteous army that occurred as a national resistance movement.
During the Japanese Invasion of Korea in 1592, the righteous army chiefs were at the top of society in the provinces and served as spiritual leaders, and economically, they were small and medium-sized landowners and had an organic connection with farmers through land. The Japanese invasion of the country destroyed their social and economic foundations.
On the other hand, the people wanted a well-known and reliable righteous army commander to fight under the command of an incompetent general under the command of a general who was forced to serve by the government. In addition, it was advantageous to go to the righteous army rather than the government army to protect parents and wives and children around the local area. Since the royal court also recognized the righteous army as a public army to urge the creativity of the righteous army, the number of participants in the righteous army of the general public continued.

In Gyeongsang province
Hapcheon (June 6, 1592): Kim Myeon and Jeong In-hong against Mōri Terumoto
Chogye (June 7, 1592): Son In-gap against Mōri Terumoto
Ucheokhyeon (July 10, 1592): Kim Myeon and Kim Seong-il against Kobayakawa Takakage
Yeongcheon (July 27, 1592): Gwon Ung-su and Park Jin against Fukushima Masanori
Uiryeong: Gwak Jae-u against Kobayakawa Takakage
Hyeonpung: Gwak Jae-u against Hashiba Hidekatsu
Yeongsan: Gwak Jae-u against Hashiba Hidekatsu

In Jeolla province
Damyang (June 25, 1592) : Go Gyeong-myeong and Yang Dae-park
Naju : Kim Cheon-il
Gwangju : Kim Deok-nyeong

In Chungcheong province
Geumsan (July 9, 1592) : Go Gyeong-myeong and Gwak Yong against Kobayakawa Takakage
Okcheon : Jo Heon
Geumsan : Yeonggyu and Jo Heon
Cheongju : Yeonggyu and Jo Heon

In Gangwon province
In Hwanghae province
Yeonan : Yi Jeong-am

In Pyeongan province
Mountain Myohyang : Seosan

In Hamgyeong province
Gilju : Jeong Mun-bu

During the Manchu Invasion of Korea
During the Jeongmyo-Horan and Byeongja-Horan, righteous army rose up in each region. At this time, the motivation for the righteous army to occur was to overcome the difficulty that was difficult to solve due to the defeat of the government army. In other words, most of them were Geunwangbyeong (근왕병: Royal Provincial Army).
During the Horan period, the righteous army rose early not only in the invaded area but also in the rear area. The righteous army activity in the invaded area was to directly fight the enemy and cause losses. The creativity in the rear area was to gather the recruited righteous army in one place and go to the battlefield to overcome the helplessness of the government army.
However, overall, the activities of the righteous army during the Horan were incomparably weaker than those of the righteous army during the Imjin War. The reason was that after the Imjin War, political turmoil, economic collapse, and social unrest continued, resulting in no sense of unity between the authorities and the people centered on the dynasty.
In fact, during the invasion, the righteous army did not see much clear activity in the area where the enemy invaded. Mock activities were carried out in the rear areas of Honam and Yeongnam, but they were disbanded when Injo gave in to the qing dynasty while heading to the northern battlefield.
For example, In Yean-hyeon, the seonbi clans of Yean-hyeon, centered on the Gwangsan Kim clan, were active in Hyanggyo. When the Jeongmyo-Horan broke out, the seonbi clans of Yean-hyeon organized and divided the righteous army around the righteous army office (兵廳廳소) by mission, and most of them focused on mobilizing the supplies rather than mobilizing the military. Therefore, the righteous army was disbanded as reinforcement was promoted with little actual military activities.

During the Japanese colonial period (1910–1945)
Late Joseon dynasty period Korean nationalism outgrew the unplanned, spontaneous, and disorganized Donghak movement, and became more violent as Japanese colonizers began a brutal regime throughout the Korean peninsula and pursued repressive policies against the Korean people.
The Japanese colonial authorities fought with rifles, state-of-the-art cannons, machine guns, repeaters, mounted cavalry reconnaissance units in the mountains, and an entrenched class of informers and criminals developed over the previous decade before the battles began.
Koreans fought with antique muzzle-loaders, staves, iron bars, and their hands. There were rare instances of modern weapons, and a few enemy weapons captured.
For at least thirteen years after 1905, small irregular forces, often led by regular army commanders, fought skirmishes and battles throughout Korea against Japanese police, armies, and underworld mercenaries who functioned to support Japanese corporations in Korea, and as well-armed Japanese settlers who seized Korean farms and land. In one period, according to Japanese records in Boto Tobatsu-shi (Annals of the Subjugation of the Insurgent), between October 1907 and April 1908, over 1,908 attacks were made by the Korean people against the invaders.
While most attacks were done using available weapons, and bare hands, international arms dealers profited. Arms dealers and governments who supplied the Korean resistance included Chinese arms dealers from across the Yalu and in coastal waters; German arms dealers provided Mausers, and a French cruiser in September 1908, resupplied Korean Catholic armies in payment for gold at exorbitant prices. Smugglers from Japan as well supplied Murada weapons, with links to anti-Meiji forces who hoped to see Ito and his clan toppled in the wake of disasters in the Japanese economy.After the Russian revolution, some weaponry was diverted from the White forces into what is now North Korea, and supporters built there, however this was sparse and while white Russian mercenaries fought against the Japanese, this was a minor element.

During the Righteous Armies Wars
The Righteous Army was formed by Yu In-seok and other Confucian scholars during the Peasant Wars. Its ranks swelled after the Queen's murder by the Japanese Samurais. Under the leadership of Min Jeong-sik, Choe Ik-hyeon and Shin Dol-seok, the Righteous Army attacked the Japanese army, Japanese merchants and pro-Japanese bureaucrats in the provinces of Gangwon, Chungcheong, Jeolla and Gyeongsang.
Choe Ik-hyeon was captured by the Japanese and taken to Tsushima Island where he went on hunger strike and finally died in 1906. Shin Dol-seok, an uneducated peasant commanded over 3,000 troops. Among the troops were former government soldiers, poor peasants, fishermen, tiger hunters, miners, merchants, and laborers.
The Korean army was disbanded on August 1, 1907. The Army was led by 1st Battalion Commander Major Park Seung-hwan, who later committed suicide, which occurred after the disbandment and was led by former soldiers of the Korean Army against Japan in Namdaemun Gate. The disbanded army joined the Righteous Armies and together they solidified the foundation for the Righteous Armies battle.
In 1907, the Righteous Army under the command of Yi In-yeong amassed 10,000 troops to liberate Seoul and defeat the Japanese. The Army came within 12 km of Seoul but could not withstand the Japanese counter-offensive. The Righteous Army was no match for two infantry divisions of 20,000 Japanese soldiers backed by warships moored near Incheon.
The Righteous Army retreated from Seoul and the war went on for two more years. Over 17,000 Righteous Army soldiers were killed and more than 37,000 were wounded in combat. Unable to fight the Japanese army head-on, the Righteous Army split into small bands of partisans to carry on the War of Liberation in China, Siberia, and the Baekdu Mountains in Korea. The Japanese troops first quashed the Peasant Army and then disbanded what remained of the government army. Many of the surviving guerrilla and anti-Japanese government troops fled to Manchuria and Primorsky Krai to carry on their fight. In 1910, Japan annexed Korea and started the period of Japanese rule.

Armies and orders of battle
Of the sixty righteous armies, the list and descriptions below follow what is known of the names of the more well-known armies and their sequential appearance in combat; individual generals and named figures are given larger biographies on separate articles which cite more historical background.

In 1895: Righteous army of Eulmi
Yi So-ung
No Eung-gyu
Gi U-man
Yi Gang-nyeon

In 1905: Righteous army of Eulsa
Choe Ik-hyeon
Min Jong-sik
Shin Dol-seok
Jeong Yong-gi
Yi Han-gu
Im Byeong-chan

In 1907: Righteous army of Jeongmi
Hong Beom-do
Yun Hui-sun
Cha Do-seon
Kim Su-min
Min Geung-ho

13 province alliance righteous army in 1908
Commander in chief: Yi In-yeong
Commander: Heo Wi
Representative of Gangwon: Min Geung-ho
Representative of Chungcheong: Yi Gang-nyeon
Representative of Gyeongsang: Park Jeong-bin
Representative of Gyeonggi, Hwanghae: Gwon Jung-hui
Representative of Pyeongan: Bang In-gwan
Representative of North Hamgyeong: Jeong Bong-jun
Representative of Jeolla: Mun Tae-su

See also
History of Korea
Battle of Namdaemun
Korean independence movement
List of militant Korean independence activist groups
Righteous Army Command
Korean Liberation Army
Battle of Qingshanli

References

William E. Henthorn, A History of Korea, Free Press: 1971