How Did Japan Occupy Korea? — The History Of A Complicated Relationship

This site contains affiliate links. If you purchase through these links we may receive a commission.

Jump To...

At about 120 miles, Korea is the closest nation to Japan. Around 250,000 Japanese tourists visit South Korea each month. Despite this, even in South Korea, people could not buy Japanese films until 2004. 

If Japan and Korea updated their relationship status, it would definitely be “it’s complicated.” For one thing, there are currently two Koreas. The current state of affairs is mostly a direct effect of Japanese imperialism in the 20th Century and World War II, but the roots actually go back much farther. A full picture of the two-millennia back and forth between the two countries is necessary to understand the tense and complex relationship we see today.

The countries had contact before Japan was even a unified country, so that’s where we’ll begin our journey. Follow it through to World War II, Korean independence, and the modern-day.

How Did Japan Occupy Korea? — The History Of A Complicated Relationship

An Ancient Alliance

In the beginning, it was the Korean people who came to and influenced Japan. In the 1st Century BC, the Korean peninsula became relatively politically stable under the Three Kingdoms. These were three separate states that divided the peninsula. The largest kingdom Goguryeo, from which Korea derives its modern name, even controlled a significant amount of Manchuria in China.

During this time, Japan was still a disunified collection of tribes. It wasn’t until about the 3rd Century AD that Japan unified under the Yamato Empire. The Yamato state had high ambitions, and they sought diplomatic relations with the major East Asian states, including China and the Three Kingdoms of Korea.

The Baekje Kingdom of Korea saw the new state as especially useful, and in the 7th Century, they formed an alliance with Yamato Japan. Together they fought the Silla Kingdom of Korea, but the Silla Kingdom was allied with Tang China, and the Silla defeated the new alliance.

After their defeat, many Baekje refugees fled to Japan, bringing Korean and mainland Asian culture to Japan. This included the Buddhist religion, which greatly affected the culture of Japan and would influence its development to the present day. 

How Did Japan Occupy Korea? — The History Of A Complicated Relationship
Kikuchi Yoosai, a depiction of the Mongol invasion on Japan

Piracy and Mongols

The refugees from the Baekje kingdom integrated into Japan and created a fundamental part of the new culture. However, Japan’s relationship with the states remaining on the Korean peninsula was strained. They had just fought against each other, after all. Then Japanese pirates began regularly pillaging the Korean coast, and things got worse.

By the 12th Century, the Mongolian Empire had become the dominant power in East Asia and most of the world. The Goryeo Kingdom of Korea submitted themselves to the Mongols hoping to rid themselves of their Japanese pirate pests.

The Goryeo King begged the Mongols to conquer Japan, which the Mongols agreed to as long as Korea provided all the necessary ships, 1,000 in total. Japan was still a young state with little power in their region. They were understandably terrified of the massive force coming to attack their island home and assumed they would be defeated. In fact, Japanese parents still repeat the phrase “mukuri kokuri, oni ga kuru” to their children similar to tales of the Boogeyman in the West. The phrase literally means “the Mongols and Koreans are coming.”

Despite the overwhelming force of the Mongol-Korean invasion, the weather saved the Japanese. Twice, the Mongols sent fleets to attack Japan, and twice typhoons came and destroyed the invaders. 

Naturally, the Japanese came to believe they’d been saved by a supernatural force, the Kamikaze, or divine wind. They decided they were a favored people protected by the Kami, their gods, and this informed their self-image as a superior nation that would become very important in their future foreign relations.

How Did Japan Occupy Korea? — The History Of A Complicated Relationship

The Tables Turn

The Japanese survived the Mongol invasion and realized they were a nation worthy of competing in the region. By the 16th Century, Toyotomi Hideyoshi, also known as the Great Unifier of Japan, decided his forces were ready to take on the Chinese.

The Japanese moved to conquer China by way of the Korean peninsula. They took over a good portion of the territory and pushed the Korean forces farther and farther north. The Japanese handily outfought the Koreans on land, but they were outmatched by the Korean navy. 

Finally, the Emperor of Ming China intervened. Chinese forces pushed back the Japanese and surrounded them in Seoul. The Japanese held there until Hideyoshi’s death. He was succeeded by the “Council of Five Elders” who considered the effort futile and ordered the Japanese forces to come home.

Although the Japanese ultimately left Korea, the effects of their conquests would last to the present. Just like Japan once feared the Koreans to the point that their invasion became a tale to scare children, the Koreans now did the same with the Japanese. Korean parents still warn misbehaving children with the saying “Ear and nose cutting devils are coming.” The gory threat remembers the Japanese practice of cutting off the noses and ears of Korean soldiers to count their kills, something that eventually evolved into doing so to living civilians in order to meet kill quotas ordered by officers.

The Japanese invasion also ransacked and looted much of the Korean nation and destroyed many important buildings. Much of the Korean heritage was erased, and their culture was altered forever.

How Did Japan Occupy Korea? — The History Of A Complicated Relationship

Sakoku Isolation

After their failed conquest, the Tokugawa Shogunate, also known as Edo Bakufu, came to power in Japan, beginning the Edo Period. They conquered competing feudal clans and solidified their power by isolating Japan under their policy of Sakoku

Under Sakoku, ordinary Japanese citizens could not leave their country, and foreigners could not enter. Trade was heavily restricted and could only be done through a few buffer zones that the Tokugawa monitored with a heavy hand. 

There was a small amount of trade with Korea, and the Koreans sent occasional diplomatic missions to Japan to maintain the peace both countries warily kept across the Sea of Japan.

How Did Japan Occupy Korea? — The History Of A Complicated Relationship

The Meiji Restoration and Imperialism

An American envoy forced Japan to open to foreign trade and influence in 1853. The Japanese quickly realized that after two centuries of isolation, they were far behind the Western powers both technologically and politically. They did not want to end up colonized like many of their neighbors.

In 1868, the Boshin War resulted in the defeat of the Tokugawa Shogunate, and the Emperor resumed supreme authority. This became known as the Meiji Restoration, and the new government did away with the isolationist policy of the Edo Period and set about to modernize Japan as quickly as possible and strengthen it against foreign forces as well as increase its influence on the global stage.

How Did Japan Occupy Korea? — The History Of A Complicated Relationship

A Misunderstanding With Korea 

As the Meiji government sought to create more complex relations with foreign powers, Korea, Japan’s closest neighbor, was top of the list. The Japanese sent a diplomatic envoy to Korea meant to establish goodwill between the two nations. However, cultural misunderstandings resulted in its having the opposite effect.

For one thing, it was a completely new regime. The Koreans were used to very restricted communication with the Tokugawa Shogunate that involved specific seals and limited access. The Meiji envoy, though, came with new seals and names. 

More importantly, the Meiji government referred to their leader as ko (皇), or emperor, unlike the term taikun (大君) that had been used for the previous Shogun. Ko was the term the Koreans used to refer to the Chinese Emperor. The Chinese were the dominant power in Asia, so the Koreans took this to mean that the Japanese saw their emperor on an even plane with the Chinese emperor. That would imply the Koreans were subjects of the Japanese.

As a result of the misunderstandings, Korea refused to acknowledge the authority of the new government and the Meiji Emperor of Japan. Tensions began to rise. In 1873, the Japanese government even proposed invading Korea to force them into recognizing the Emperor’s authority, but the proposal was ultimately rejected.

How Did Japan Occupy Korea? — The History Of A Complicated Relationship

Japanese Protectorate

International relationships were getting complicated across the Sea of Japan. While Japan was modernizing as fast as it possibly could, adopting new technology, and building military and political might, the other Asian powers were declining.

Qing China’s power was weakening due to Western colonization, and Russia was gaining influence in the Korean peninsula. Japan took the opportunity to strike and expand its empire, in part to gain access to important resources it lacked in its island nation, and in part to give all the Samurai something to do.

The Japanese easily defeated Qing China in the First Sino-Japanese War and demanded that Korea be considered an independent state. They then drove Russian influence from the peninsula in the Russo-Japanese War, which the Japanese also won.

This set up Korea as a protectorate of Japan. Korea was still its own country with its own government, and for a while, Japan stayed out of its affairs for the most part.

How Did Japan Occupy Korea? — The History Of A Complicated Relationship
A written copy of Japan-Korea Annexation Treaty

Japan Annexes Korea

Things changed in 1910 when Japan imposed the Japan-Korea Annexation Treaty on Korea. This made Korea a part of the Japanese Empire, and it lost all its sovereignty.

The annexation of Korea was essentially Japan trying to flex its new power, and it was wildly successful. The British and American governments accepted the treaty and annexation without any complaint. It seemed that Japan had become an imperial force to reckon with, setting the stage for the world wars to follow.

How Did Japan Occupy Korea? — The History Of A Complicated Relationship

World War II

During World War II, Japan used Korea for natural resources important to the wartime economy and as their point of access for the main Asian continent and their campaigns there. Japan also imported millions of Korean workers during World War II. Many of these were voluntary immigrants, but others were coerced. 

By 1942, there were major labor shortages in Japan. Most young males were off fighting in the war, and the empire needed as much industrial output as possible to feed its war machine. The Japanese government passed the National Mobilization Law which officially drafted Koreans to work in factories, mines, or wherever they were needed. 

Most of these conscripts remained in Korea, but the Japanese government forcibly relocated about 670,000 to Japan. Their working conditions were poor, and it’s estimated that nearly a million Koreans died working in Manchuria, Korea, and Japan.

Surprisingly, Japan did not force Koreans to fight at first. This was reserved for ethnic Japanese men. However, by 1944, Japan was losing the war and needed all the soldiers they could get. The Japanese conscripted all Korean men, sending some of these to combat against Allied forces. 

How Did Japan Occupy Korea? — The History Of A Complicated Relationship
A signed copy of the Treaty On Basic Relations of Japan And The Republic Of Korea

Korean Independence

Despite various independence movements, Korea did not gain independence from Japan until the end of World War II. Japan surrendered to the United States in August 1945. While the US left the Japanese Emperor in power, they liberated any of Japan’s conquered territory, including Korea.

Following their occupation of Japan, American forces also landed in the south of Korea. Soviet forces had already advanced into the north of the peninsula. The two powers failed to come to an agreement involving the organization of Korea and its new government, so the country remained divided into north and south, albeit independent of Japan.

How Did Japan Occupy Korea? — The History Of A Complicated Relationship

Effects of Japanese Imperialism on Korea

Japan’s occupation and rule of Korea dramatically changed Korean society in a way that is still evident today.


By the time of annexation in 1910, Japanese people owned nearly 10% of all the arable land in Korea. Under complete Japanese rule, this increased to over 50% in 1932. The Japanese placed heavy taxes on the Koreans to pay for the industrial improvement of the Korean agricultural system, and as a result, many Korean farmers lost their land or became tenant farmers paying rent to Japanese landlords. This was rarely enough to cover all their taxes, though, and many Korean farmers had to send their wives and daughters to work in factories or as prostitutes to get by.


The Japanese had a strong policy of preservation, but much of Korea’s heritage was still destroyed. For example, in 1911, the Japanese tore down the Gyeongbokgung, the Korean royal palace, to build their administrative headquarters. 

Tens of thousands of cultural artifacts disappeared from the country. This issue continues to the present day. The government of Korea asserts that Japan still has almost 35,000 cultural artifacts that the country stole from Korea. Many of these are owned by private citizens, but some are on public display, such as those in the Tokyo National Museum. 

The Japanese also introduced a household registration system in Korea. They abolished the Korean caste system and forced the Koreans to change from their traditional clan-based naming system to the Japanese surname system. Around 80% of Korean families changed their names hoping it would help their children in the future.

Language and education

At the beginning of Japanese colonialism, the Japanese government supported the Korean language. It was taught in schools, and the Korean Language Society promoted its use in media and literature. However, the Japanese did actively change the language by shifting the writing system from Hanja, a Korean adaptation of Chinese characters, to a mixed Hanja-Korean system much like Japan’s.

Once World War II started, the Japanese attitude completely reversed. The Japanese had instituted a free public education system designed to control the population and produce model “Imperial Citizens.” The government decided on a policy of assimilation, and they used the school system to limit the Korean language. Private schools were mostly divided and destroyed if they taught anything “patriotic.”

The Japanese also banned public newspapers and made it much more difficult for Koreans to publish books than Japanese. The Japanese government had further plans for restriction, but they lost the war before they could enact them.

War crimes

Japan used a heavy hand to maintain its colonial authority. Resistance fighters or anyone even protesting Japanese rule were dealt with harshly. The military often came to put down demonstrations and often killed protesters, sometimes by horrific means.

During World War II, many Koreans were used for conscripted labor in Japanese territories. About 450,000 men were forced to go to Japan and work. The conditions were dangerous and poor, and hundreds of thousands died.

One of the most well-known examples of conscripted labor is that of comfort women. The Japanese military conscripted young women, usually from rural areas, for labor, but instead of sending them to a mine or factory, they employed them in brothels for Japanese soldiers. Nearly half a million Korean women ended up in these brothels. Less than 50 are still alive.

How Did Japan Occupy Korea? — The History Of A Complicated Relationship

Modern Relationship

Things are still tense between Japan and South Korea. 37% of Japanese people view South Korean influence negatively, and 79% of South Koreans view Japanese influence negatively. After World War II, South Korea even banned cultural imports from Japan, a restriction that lasted until 1998. South Koreans couldn’t import Japanese CDs or DVDs until 2004.

Tensions have also risen in recent years due to various symbols and their reflection on Japanese colonialism. For example, South Korea protests to the name “Sea of Japan,” while Japan contests South Korea’s claim to the Liancourt Rocks, a small group of islands occupied by the South Korean military. South Korea also does not believe Japan has adequately apologized for the practice of comfort women.

Despite the bilateral suspicions, it can be said that Japan and South Korea at least maintain a reluctant alliance. Both nations are close allies of the United States, and both nations rely heavily on US military support. Especially militarily, the countries work together with the US, though there are plenty of complaints on both sides, even leading to South Korea’s pulling out of the General Security of Military Information Agreement in 2019.

North Korea is another story. There are no formal diplomatic relations between the two countries. Japan regularly accuses the country of abducting its citizens and testing missiles through their airspace, and North Korea threatens Japan with force.

91% of Japanese people view North Korea’s influence negatively, the most negative perception of North Korea by any country in the world. Recent testing by North Korea of nuclear-capable missiles into Japanese waters has continued to sink the relationship between the two countries.

As the relationship between North and South Korea evolves as well as the relationship between the two Koreas and China and the United States, the complexities of the Japanese-Korean relationship will become increasingly important. Only time will tell how it will play out.

You may also like
Share This Article

Leave a Comment