When it comes to the Sui Dynasty Emperor Yang Guang, people's first reaction must be absurdity. Although the Beijing-Hangzhou Grand Canal, which he ordered people to build, brought happiness to future generations, it caused the innocent deaths of millions of Zhuangding at that time. In addition, the three eastern expeditions to Goguryeo triggered by him made the people even more miserable.
For this crusade, people have always had a doubt: as the hegemon of the Central Plains at that time, the Sui Dynasty's military strength was ten times that of Goguryeo, why was it defeated?
In fact, it is not rare for ancient and modern Chinese and foreign battles to win more with less, such as the Battle of Chibi, the Battle of Guandu, the Battle of Julu, etc., so it is not surprising that the Sui Dynasty's Eastern Expedition failed. The outcome of a battle is the result of an interaction between the two opposing sides. Simply put, the Sui Dynasty defeated Goguryeo three times both because the Sui Dynasty did not look so strong, and because Goguryeo did not look so weak.
When the Sui Dynasty attacked Goguryeo, it actually faced a crisis of internal and external troubles. Internally, it not only had to suppress the people who resisted under the exploitation of tyranny, but also had to deal with the collusion and conspiracy between the Yuwen clan of the Northern Zhou Dynasty and the warlord forces in the DPRK and China. In fact, the Sui army had already attacked Liaoyang during the second conquest of Goguryeo, but due to the rebellion led by Yang Xuangan in the country, the Sui army was forced to retreat. However, on the way back, he was repeatedly blocked and ambushed by Goguryeo, and suffered heavy losses.
Externally, in addition to confronting Goguryeo, it also had to solve the hidden disturbances of other regimes around it. During the Eastern Expedition to Goguryeo, nomadic and ethnic minority regimes such as the Jing dynasty and Fuyu often intercepted the logistics of the Sui army. Even during the defeat and retreat of the Sui army, these regimes would take advantage of the fire and loot. Moreover, before the Eastern Expedition, the Sui Emperor successively dug the Grand Canal and "inspected" The lower Yangzhou, the national strength was very expensive, and in order to reflect the wealth and strength of the Sui Dynasty, he vigorously rewarded the surrounding ethnic minority regimes for a long time, and the national wealth had long been consumed.
In fact, the most fatal defeat of the Sui army was that the Eastern Crusade was a long way away, so that the front line was elongated and communication was inconvenient; the cold climate of the Korean Peninsula caused the soldiers to be sick. As we all know, Zhuge Liang left qishan six times, but several times he gave up because the battle line was too long and the supply of grain and grass was insufficient. The Sui army was also facing logistical problems, one was that the Sui army was growing stronger, the material demand was very large, and the transportation was quite difficult; the second was that the road was far away, the land it passed through was often looted, and the supply was very difficult; third, the Sui Dynasty's shipping technology was limited, and it was difficult to rely solely on small boats and temporary sea ships to ensure the supply of transporting millions of troops. To this end, the Sui Emperor had to change his tactics, and he ordered his soldiers to carry their own grain and grass. This does alleviate logistical problems to some extent, but it increases the burden on soldiers on the front lines. Because of the food and grass, the soldiers' marching speed and combat ability were greatly reduced. Coupled with the harsh climate in the Eastern Liaoning region, many soldiers had fever, diarrhea, headaches and other symptoms, so they had to throw away grain and grass. After entering the hinterland of Goguryeo, the supply of the Sui army was even more difficult. In the case of running out of food and grass, the staggering number of troops naturally has no combat ability. In addition, the Sui army originally adopted the strategy of land and sea attack, that is, the army attacked Liaoyang, the navy landed from the goguryeo flank and directly approached Pyongyang, and then the two armies assembled under the city of Pyongyang to form a siege. This combat deployment may seem reasonable at first glance, but in reality the two armies are far apart and extremely inconvenient for communication to form an effective alliance.
In contrast, at that time, Although Goguryeo was no more territorial than the Sui Dynasty, its power and economy were very stable. During the Southern and Northern Dynasties, Goguryeo took advantage of the chaos in the Central Plains and constantly annexed the Liaodong region, so that the national strength increased greatly, and its strength should not be underestimated. It took the Sui and Tang dynasties decades and many failures to finally destroy Goguryeo.