A little background leading up to the 2nd invasion: The northern Zhou dynasty fell as Yang Chien(a.ka. Wen ti) took over the throne, and renamed it Sui in 581 A.D. Sui also invaded the southern chinese dynasty of Chin in 589, destroyed it and unified China. This was the first unified chinese empire in 400 years. Yang Chien was an ambitious dude, and koguryo's diplomats warned koguryo's kings that Yang chien could possibly dream of an invasion, judging by his ambitious character. There was also a rule that whenever china unified, it was a threat to its neighbors, so all of china's neighbors were at high alert of their security, and paid tribute to Yang Chien.
Their predictions were on the spot as Yang turned his eyes to the north after the unification, and demanded tribute from the Turkish empire and Koguryo. The turks submitted to his pressure, but koguryo refused. Many times Yang sent spies and delegates to koguryo and demanded tribute, but koguryo ignored it. Soon, koguryo was the only nation bordering Sui that didnt pay tribute. Yang was furious, and prepared an invasion.
Upon notice that Yang was gathering 300,000 troops for koguryo, koguryo launced a preemptive strike across the Liao river with 10,000 magyar(manchu) troops in 598. Yang responded by launching the invasion, across the Liao and the Bohai bay. Upon receiving an insulting letter by the Sui, koguryo's king and generals decided that instead of responding with the pen, "they shall respond to such disgraceful treatment with the sword". The Liao division in the north failed because of the rainy season, which stopped their supplies from connecting. The seaborn army met Kang Ishik of Koguryo and lost most of their troops and ships. The Sui retreated, and Yang put his generals in jail out of anger.
2 Koguryo offered a peace treaty, and Sui took it gladly. For a while there was peace. Paekche offered Sui help in invading koguryo (since paekche knew koguryo geography by heart, from the hundreds of years of war), but Sui refused to invade. This just resulted in koguryo attacking paekche (and Shila), a resumption of an ages-old hanbando front wars, and assaulted both countries' northern fortifications to insure they wouldn't attack in the case of another Sui invasion. Koguryo took 3000 prisoners from Paekche.
Meanwhile, the Sui royalty faced a major conflict between Yang and his son, Yangdi, resulting in the son killing his father and taking the throne (604). This meant the end of peace, because Yang junior was even more ambitious than his father. He constructed a canal between beijing and the sui capital, and reinforced the Turk's tributary status by visiting the turkish capital with his army, and forcing their king to visit Chang'an. He also demanded tribute from koguryo, the only "rogue" state, and demanded that koguryo's prince visit his palace on his birthday, but koguryo ignored his requests. Yangdi decided to launch an invasion that koguryo couldn't possibly stop, to do what his father failed to do.
Koguryo prepared for the worst by invading shilla and paekche to deter a possible two-front war, and took their northern fortifications, weakening both's military.
In the April of 611, Yangdi gathered troops from all over China and prepared for a 2nd invasion, organizing at Beijing. The total number of troops for the koguryo invasion was 1,133,800 men. He began the invasion in January of 612. The following excerpt from Sui archives (隨書) describes the greatest presentation of force in chinese history:
- The army was organized into the Left Army and the Right Army, each with 12 divisions, total divisions being 24. In each division there was a senior commander and secondary commander. The troops were organized into Da and Dan, Da being 100 men and Dan being 10 Da. Each Dan had different colors in their helmet straps and flags of their own. A division contained 40 Da of cavalry and 80 Da of footsoldiers(spearmen), which was divided into 4 Dan with a captain each.
They started marching division after division, leaving 40 li (20 km) distance between each. Trumpets and drums were played between every division. The army's flags from one end to the other stretched 960 li (480 km). The emperor himself with 6 divisions followed behind, which itself stretched 80 li (40km).
It took 40 days for the entire army to start marching. This was the greatest military show one has ever seen. -
The left army, which included the emperor's army, went to koguryo via the northern route, crossing the liao into koguryo territory in manchuria. The Right army crossed the ocean via the Shandong penninsula, attempting to reach koguryo's capital directly by climbing the river.
Yangdi's left army penetrated koguryo's defenses on the other side of the Liao river, and koguryo's troops retreated into the Yodong(Liaotong) fortress. For months the chinese couldn't capture the grand fortress, which had very high walls. Summer came and Yang vent his frustration on his generals, and diverted his troops to attack another fortress instead, the Yukhap fortress, but it couldnt be captured either.
Meanwhile the Right Army finished its shipbuilding and set sail. It's captain Lai hao wo commanded the ships, and they arrived at koguryo's shores and Lai started up the river towards the capital with half the armada. They were only 60 li from the capital when koguryo troops started to harass them. The koguryo troops feigned defeat and retreat, and Lai chased after the bait. By the time he realized that his armada was tricked into entering too deep into enemy territory, his armada was surrounded. The surrounding troops attacked at once, and the panicked Lai ordered frantic retreat. However koguryo troops were hiding all along the river in places the ships were expected to retreat to, all the way down to the ocean, and Lai's armada was thoroughly demolished. Lai himself survived and returned to the rest of the troops anchored at the sea.
While the right army lost half of its forces, the left army was making little progress and incurring heavy costs in manchuria. The lead army lead by the two Wu generals decided to go around the koguryo defense and headed towards the capital. Their army consisted of Sui's 305,000 finest troops.
General Ulchi Mundok, upon the koguryo king's order, walked into the enemy camp alone and met the two Wu generals. This highly daring tact was made despite the fact that Yangdi ordered all of his generals to kill koguryo's king or Ulchi Mundok on sight. This type of daring individual risk and sacrifice was common among the three korean kingdoms who warred with each other. Ulchi Mundok's bravery surprised the Sui generals, who were confused as what to do when Ulchi Mundok offered a surrender. Mundok requested their army to retreat, in promise that koguryo's king would follow them to the palace to establish tributary relations. The Wu generals let him go, and soon after Mundok left their camp, they regretted it. The Sui army pursued Mundok.
This was all calculated and expected by Mundok, who lured the sui army deep into koguryo territory. Although one of the generals insisted that they wait for the supply line, the other insisted on taking koguryo's capital by the end of the day. A favorite of Yangdi, he wanted to please Yangdi so badly that he wanted to be able to send a victory notice that night. Of course, Ulchi mundok knew Wu very well enough to predict this behavior. As Sun Tsu says in the ARt of War, "know thyself and thy enemy and you will win a hundred battles". Yangdi failed to understand the koreans' resolve, believing in overwhelming numerical superiority alone, which was why the 1 million-man army wasn't very effective against an enemy that knew them so well.
As the Sui army advanced deep into koguryo territory, still in pursuit of Mundok, it faced 7 battles with small dispatches of koguryo troops, all of which the Sui won. All of which, under Mundok's plan, was feigned defeat and retreat. This the Wu generals did not realize, and with their troops' morale high but stamina/supplies dropping, they set camp 30 li outside of the capital, by the Salsu river.
Ulchi Mundok sent a now-famous letter to General Wu, which said the following:
Your brilliant strategies have ascended over the heavens,
and your tactics have shaken the earth,
you have won the battles and accomplished high standards,
so why not be satisfied and go back home
The Sui generals realized that their supplies ran thin and their troops were tired, indeed too tired to capture the capital, and turned around. When the 305,000 men started crossing the Salsu river, Ulchi Mundok and his troops attacked from both sides of the river.
The result was a massacre of a truly grand scale. Nowhere to run, trapped, and scared, the Sui troops started to run for their lives in all directions, jumping into the water. Out of the 305,000 men of the Sui lead army, only 2700 went back home alive.
As news of Wu's defeat reached Yangdi and Lai(of the right army), Lai immediately set sail for china, and Yangdi retreated with general Wu locked up in chains.
2 The second invasion thus ended in complete failure for the Sui, and it cost the new empire so much that it bankrupted it. Even so, the vain Yangdi attempted two more invasions, both of which he had to turn back because of widespread rebellion across the empire. He wanted to invade again, but his advisers all voted against it, and talked him out of it. Eventually the Sui collapsed, as rebels assassinated Yangdi and the empire split up, lasting only a decade after starting out with high expectations and hopes for a unified chinese hegemony.
Talk about wartime presidential popularity. Bring the troops home!!
Also notable is the fact that Paekche was supposed to help Yangdi in the invasion of koguryo. However, as yangdi's million-man army poured into koguryo, with all bets on yangdi, paekche merely watched. Either it didnt feel the need to help yangdi, or more likely, it knew that koguryo's demise would also mean its own demise. Therefore as much as paekche and shilla hated koguryo, they tacitly knew that the entire korean penninsula and the korean people's destiny rested on her shoulders.
