Yang Di conquered Koguryo, a small country, with a million troops. Why did he come home in a fiasco?

Successive dynasties were faced with the problem that neighboring small countries and nomadic tribes invaded and plundered the border. However, when launching a counterattack, we will find that sometimes, although the national strength of the Central Plains Dynasty far exceeds these small countries, it may not be able to win or win the war. This phenomenon is largely due to the lack of strategy and tactics.

Comparing the war against Koguryo in Sui and Tang Dynasties, we can most intuitively see the important role played by correct strategies and tactics in the war.

The war against Koguryo in Sui and Tang Dynasties lasted for nearly 70 years. Emperor Wendi, Yang Di, Emperor Taizong and Tang Gaozong all conquered Goguryeo, and the scale of the war was also very large, but the achievements of the two dynasties in the war were quite different. Therefore, in the larger Sui Dynasty, the national strength was seriously damaged, and Emperor Yang died. However, the Tang Dynasty chose the correct strategy and tactics in the war, and finally won a great victory in Gaozong and destroyed Goguryeo. So, what strategies and tactics did Emperor Taizong and Emperor Gaozong and his son adopt, and achieved results that Yang Di's millions of troops could not achieve?

To answer this question, we must first introduce Koguryo. Koguryo is a small country established in the northeast of China, mainly composed of Fuyu people and other small tribes. It has a long history and has existed since the Han Dynasty. Koguryo people have a mode of production that combines agriculture with nomadism, and have the ambition to expand. They coveted the fertile soil of Hansi County, which was established by the Han Dynasty in Liaodong and the Korean Peninsula at that time, and invaded the rule of the Han Dynasty in the northeast for many times.

The reality is cruel. Goguryeo, who had ambitious expansion, was hit by the Han Dynasty. Later, Gongsun Du, a warlord of the Han Dynasty, was burned many times in Liaodong, Cao Wei, Youzhou, Wu et al. However, Goguryeo's wicked heart never dies, and finally, under the chaotic situation in the Central Plains, it gradually grew and annexed Liaodong and Han four counties on the Korean Peninsula.

When the Sui Dynasty was established, Koguryo had become a hegemonic country in Northeast Asia, with a hundred officials' dynasty, land area and grain output comparable to many Guanzhong areas, and its culture was the same as that of the Central Plains. Even more exaggerated, Koguryo also built the Great Wall. Goguryeo was a sword hanging over the head of the Sui Dynasty, and it was possible to stab it in the Sui Dynasty at any time, or even compete in the Central Plains.

So Emperor Wendi of Sui Dynasty issued a threat to warn King Koguryo to be honest just after destroying Chen. However, Koguryo people did not take Wendi's warning to heart. Instead, he sent envoys to flirt with Turks many times and collude with each other. When Emperor Wendi of Sui heard the news, he immediately organized Sui Jun to attack Koguryo with 300,000 troops. However, Wendi's conquest in the Warring States period was accomplished because of extreme weather and military epidemic, which wasted a lot of financial and human resources.

When Yang Digang ascended the throne, the national strength of the Sui Dynasty reached its peak, with 8.7 million households in the country, and the original arch-enemy Turkic had also surrendered. It is estimated that Emperor Yang Di thought that his father, Emperor Wendi Sui, did not achieve any success in the war against Koguryo because he mobilized too few troops and inherited such a strong national strength. If he doesn't make good use of it, it is a waste of time. Therefore, Emperor Yang Di issued a rare war mobilization order in the history of China.

In the seventh year of the Great Cause (A.D. 6 1 1 year), Yang Di ordered all the military forces in the world, regardless of the distance between north and south, to assemble in Zhuojun County, with a million-strong army under the personal command of Yang Di, and when they went to war, the troops even carried flags for more than 1,000 miles. This huge army organized by national mobilization was defeated by Yang Di's wrong command. Emperor Yang Di ordered Sui Jun to advance and ordered that if Koguryo troops surrendered, they would be appeased. This made Sui Jun often pretend to surrender when the city was about to break, but continued to resist after the city was built, causing heavy casualties in Sui Jun. Yang Di, who was defeated and returned to China, was unwilling to organize the second and third expeditions immediately. It wasn't long before 600,000 troops went to the battlefield. The country was in turmoil because it could not bear the huge consumption brought by the army expedition. The peasant uprising was surging, so Emperor Yang Di had to move troops to return to China, and the country soon perished.

After the chaos in the world at the end of Sui Dynasty, the Tang Dynasty was established. During the period of Emperor Taizong, there were only 3 million households in China due to the huge consumption caused by the civil war at the end of Sui Dynasty. It can be seen that the national strength and resources that Emperor Taizong could use to attack Koguryo were far less than those during the reign of Yang Di. However, Emperor Taizong believed that Liaodong was a native of China, and Koguryo did great harm to future generations. If it can't be carved by the roots in time, it will inevitably become a catastrophe in the future.

Thus, in the eighteenth year of Zhenguan (AD 644), Emperor Taizong resumed the battle of Liaodong after Sui Wen and Emperor Yangdi. Emperor Taizong used personal expedition, and Tang Jun went hand in hand by land and water. In the first battle, Liaodong City was recovered and 20,000 Koguryo troops were captured. Then Emperor Taizong defeated Goguryeo150,000 reinforcements who came to rescue Anshi City, which shocked Goguryeo all over the country. Later, due to the supply of grain and grass and the cold weather, Tang Jun began to retreat. Although Tang Jun, led by Emperor Taizong, broke ten cities in succession and killed more than 40,000 people in this campaign, and achieved great results, it still failed to achieve the strategic goal of Emperor Taizong's complete elimination of Goguryeo.

After returning home, Emperor Taizong and his ministers summed up the experience of fighting Goguryeo in the Central Plains Dynasty, especially the lessons of Yang Di's three failed expeditions, and finally formulated new tactics that had never been implemented before. In other words, although Goguryeo is not small in physique, her national strength is still not as good as that of the Tang Dynasty. Therefore, instead of launching a large-scale conquest, Emperor Taizong organized a small group of partial divisions to harass and go deep into its border, and carried out large-scale killings at the critical moment of its production, which constantly consumed its national strength, making Goguryeo tired of coping, but too busy to take care of it.

The harassment strategy re-formulated by Emperor Taizong played a great role. From 647 to 649, Tang Jun attacked Koguryo many times and won great victories. Slowly, Koguryo's national strength is getting weaker and weaker, while Tang Jun is getting stronger and stronger. In the first year of Ganfeng (AD 666), when the time was ripe to attack Koguryo, Tang Gaozong ordered Tang Jun to attack Koguryo separately. The attack was exceptionally smooth, and Tang Jun was invincible. On September 12 of that year, Tang Jun attacked the capital of Koguryo and divided it into nine counties. Twenty thousand Tang Jun led by Xue guarded Pingyang, Anton was the protector, and Koguryo was completely destroyed.

Comparing the Sui and Tang Dynasties' attacks on Koguryo, we can see that in this protracted war, the four emperors of the two dynasties spent a lot of energy to organize troops to attack Koguryo, while Yang Di, who had great national strength and military power, failed in three expeditions, wasting national strength in vain and leading to the collapse of the country. On the other hand, Emperor Taizong formulated effective strategies and tactics, which constantly consumed national strength and made Goguryeo exhausted. Finally, he was destroyed by Emperor Gaozong. From this point of view, the rationality of strategy and tactics is directly related to the outcome of this war against Koguryo.