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Japan’s Invasion of Korea – 1592-1598

“A Dragon’s Head and a Serpent’s Tail” by Kenneth Swope (2009) at

Korea historically has been uninterested in waging war on its neighbors. The country has an easily defined northern border (mountains in the center, the Yalu river to the northwest, and the Tumen river to the northeast; in all other directions Korea is surrounded by the sea. When Korea unified under the Silla Kingdom around 670, the natural borders gradually solidified in people’s minds, though the northern border was rarely peaceful. 

After the Joseon Dynasty took control of Korea in 1394, the country experienced nearly uninterrupted peace for the next ~200 years – and then Japan invaded. 

Japan’s invasion of Korea in 1592 is a very strange event in world history. Never before had Japan launched an invasion of a nation beyond the Japanese islands. After the unsuccessful Korean invasion, the Japanese only attacked on other nation in the next 280 years (the Ryukyu Islands in 1608).  

The Japanese invasion is not often talked about in the US and it doesn’t have a very clear narrative, nor does the invasion make much sense. At the end, the Japanese withdrew as did the Chinese, who came to help the Koreans, leaving Korea battered and bruised, from a war which was not even aimed at them.  

Incredible as it seems, Japan’s stated goal for the invasion of Korea was the conquest of Ming Dynasty China – when it was the richest and most populous nation in the world. Conquest of the Ming seemed insane to most people, not only in Japan but in Korea as well. Yet, as history would subsequently reveal, the Ming Dynasty was conquered about 60 years later by small, but highly capable military force from the northeast. This was the Manchu under Prince Dorgon who conquered China and subsequently ruled the huge nation for 270 years (roughly 1648 till 1911). 

Despite the stated Japanese intentions, they never set foot on Chinese territory; the army Hideyoshi sent to conquer China did not come within 100 miles of China’s border. Instead all the fighting took place within Korea and the coastal waters off southern Korea. 

Professor Kenneth Swope has written the best book on the war, titled “Dragon’s Head and Serpent’s Tail” (available here from Amazon). It explains the war clearly and describes the battles and equipment of the three sides (Japan, Korea, and the Chinese who came and helped defend Korea with a massive army and fleet). It is widely acknowledged that the Ming government under the Wanli Emperor’s direction saved Korea from what would have been a permanent Japanese occupation (Swope, pg. 285). Although Korean soldiers and ships fought heroically against the Japanese, it was the Chinese army in conjunction with the Korean-Chinese fleet that forced the Japanese to retreat. 

For all their efforts – more than 35,000 soldiers dead, several million ounces of silver spent – the Chinese received (and asked for) no reward. The Ming government paid most of the money required to keep their army supplied in Korea, and when the war was over, they pulled their army out, leaving the border with Korea unchanged. The Ming even supplied a large amount of food to help keep the Koreans people from starvation. As the Ming government said, the Koreans had been a faithful and peaceful vassal state for nearly a thousand years, obviously they should be protected from the unprovoked attack by the Japanese barbarians (Swope, pg. 126).

There are a number of notable battles in the Korean war. One is the battle of Pyongyang in 1593. In this battle, the Chinese army, fresh and well trained, took up positions around the fortified city of Pyongyang, defended by more than 20,000 Japanese samurai. The attack was a masterpiece of an assault on a fortified position, with cannons breaking down the gates using concentrated fire, along with Korean saboteurs who snuck inside the city and set fires and heroic Korean monks who charged into battle at the vanguard of one of the assault columns. By the end of the day, the Japanese gave up the city and fled south in a chaotic retreat. More than half their army died (Swope, pg. 156). For the rest of the year, the Japanese were constantly in retreat from the Chinese army, they abandoned Seoul, the capital, without a fight as they retreated to the coastal areas.  

The next interesting land battle was the siege of Ulsan in 1597 (near the southern port city of Busan). This operation started out well, with the Chinese & Korean army of some 55,000 men surrounding the Japanese defenders of some 20,000. The Japanese did not expect the Chinese to attack them at Ulsan and so the defenders had little supplies (Swope, pg. 256). In the first week, the Chinese nearly breached the inner fortress but the Japanese managed to reinforce Ulsan by sea and after two weeks, the elite Japanese troops which arrived from Busan counter-attacked the Chinese- Korean army and forced them retreat with heavy losses. (Swope, pg. 259) But the Japanese were apparently so worried about the massive Chinese army still intact in southern Korea, that they made no attempt to follow up this victory with an offensive of their own.

The last battle is the sea battle of Noryang Straits. The Korean fleet was, once again, under the command of their great admiral, Yi Sun-sin. The Chinese fleet of similar size had two highly experienced commanders and a number of huge ships armed with big cannons. The Koreans and the Chinese ships relied on their cannons to sink the Japanese while the Japanese consistently tried to close with their enemy’s ships and board them. The battle was a complete victory for the Korean-Chinese fleet, as more than 200 Japanese ships were sunk. However, the Korean Admiral Yi died from a bullet wound while one of the two Chinese commanders also died when the Japanese managed to board his flagship and kill everyone on board. 

Noryang Straits was the last battle of the war; by early 1599 the Japanese had abandoned all their forts in Korea. Hideyoshi, the warlord of Japan, had died four months earlier, and the Japanese had been slowly withdrawing from Korea even before his death. (Professor Swope argues that Hideyoshi ordered the retreat from Korea before his death in the late fall of 1598 [Swope pg. 266]. If so, the Japanese were quite dilatory in their retreat since the battle of Noryang straits took place in mid-December). 

Key points: without question, the Japanese feared the Ming army. The Ming had a massive advantage over the Japanese in heavy cannons and in supplies. Also, the Ming government was highly skilled in moving troops and supplies over long distances. It seems the Japanese respected the Chinese soldiers as near equals in hand to hand combat. On water, the Japanese ships were nothing more than fishing boats loaded with samurai and apparently rarely armed even with small cannons. They were defeated time and again by the Korean and Chinese navy.

On land, the Ming & Korean military had only a few outright victories to their name. The Japanese samurai army won most of their battles. Given their numbers and their tactical superiority, Japan seemed to be in a position to annex all of Korea, and yet they failed. 

The greatest weakness of the Japanese invasion force came from the very top. The Japanese leadership was missing in action. The Japanese army had no operational goals which made sense. Because the over-all goal of the campaign seemed implausible (conquest of China) it seems they could not create any rational operational goals.

What were the Japanese actually trying to do in Korea? A realistic goal would have been “conquer Korea and annex it”. The Japanese probably could have done this by the fall of 1592 but instead they dithered, and stayed far from the Chinese border while advancing into Manchu territory (where Nurhachi and his nascent Manchu army seems to have beaten the Japanese and driven them back to northern Korea). 

When the main Chinese army arrived in Korea in 1593, and after the defeat at Pyongyang, the Japanese retreated all the way back to the southern coast. This despite their superior numbers and their frequent victories over the poorly led and poorly equipped Korean forces. A capable Japanese leader could have struck at the advancing Ming army from different directions as it advanced south. Instead the various Japanese generals passively retreated towards the coast and opened up peace negotiations with the Ming leaders. Given that the Japanese invaded Korea as a prelude to attacking China proper, these peace negotiations tell me that the Japanese leadership in Korea had no interest in following Hideyoshi’s grand invasion scheme. You don’t negotiate a peace treaty with a country you say you are trying to conquer!

By contrast, the Ming were negotiating with Japan because time was on their side, they had a population fully ten times larger than Japan, with an economy which was even larger (per capita) than Japan’s. Potentially, the Ming could have sent half a million soldiers into Korea. In addition, the Ming could have launched their own counter-invasion of Japan (and they probably should have). 

During the second Japanese invasion, which was launched in 1597, the Japanese advanced slowly, even reluctantly. When the advancing Samurai forces suffered a minor reverse at the battle of Jiksan in October, the Japanese retreated – again – to their forts along the southern coast and waited, passively. This behavior strongly indicates the Japanese generals had no intention to trying to conquer China. Instead it looks like they were paying lip-service to the ailing Hideyoshi’s orders to attack.

For both invasions, the Japanese never had unified military leadership. Hideyoshi announced at several large assemblies that he would come to Korea to lead the Japanese army, but in the seven years of war, he never once crossed the sea to Korea. That left the Japanese commanders free to act quite independently of each other. Since Hideyoshi was the supreme commander and instigator of the invasion, the blame for failure rests heavily on his ineffective military leadership. The skill Hideyoshi had previously demonstrated in continuing Oda Nobunaga’s campaign to unify Japan, seems to have deserted him by 1590. To be blunt: Hideyoshi – in command of one of the largest armies in the world in the 1590’s – lost the war. 

Further, the Japanese acted with barbaric cruelty towards the Korean population, slaughtering men, women, and children, in massive numbers wherever they went. They enslaved thousands of Korean women. They burned and destroyed towns and sacred tombs. In just about every way, the Japanese caused the Koreans to hate and fear them. One could easily argue that the Japanese behaved like savages. 

The inability of the Japanese army to treat the Korean civilian population with even limited humanity, turned the Korean people against them. Within weeks of the invasion in 1592, large forces of Korean volunteers self-organized and fought against the Japanese. And all this when the Japanese stated they were trying to conquer China. This was not a war to punish Korean aggression (which was essentially non-existent), so why treat the Korean people with such cruelty? Ancient generals from two thousand years ago knew that if you wanted to run your supply lines through potentially hostile territory, you did your best to placate the locals people. The Japanese army went out of their way to incite the Korean people into desperate armed resistance to the Japanese invasion. (For an interesting though narrow take on this, one can read JaHyun Kim Haboush’s book The Great East Asian War and the Birth of the Korean Nation). Ms. Haboush argues that Japan’s invasion created the modern nation of Korea.

At the end of the war, the Korean government assessed their population and the land for taxes. The government found the population had fallen by as much as 20% (meaning some 2 million people had died or gone missing in the seven years of war). The Korean farmers produced just 1/3 of their pre-war production due to the ruin of their fields. 

Colin Glassey – 3/18/2020

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