Even if the war between the two countries is fierce, it will not be killed, which is an unwritten rule set in the Spring and Autumn Period and the Warring States Period. In 696 BC, the Song Dynasty people ambushed the envoys of the Chu State, and later the King of Chu felt very angry when he found out, so he directly sent troops to besiege the Song State for a full 9 months, that is, after this incident, this rule was introduced. In the history of more than 2,000 years after that, no matter which country has always kept this principle in mind, but only during the Han Dynasty, many envoys were killed by people from other countries.
In fact, the whole thing was broken because in 156 BC, during the reign of Emperor Wu of Han, there was an emissary called ShiHe, at that time, the Goguryeo power was very strong, and they also encouraged the Han Dynasty to settle in the local area, which did attract many Han People.
When Emperor Wu of Han learned of this, he was afraid that the Han Chinese would go overseas at that time, which would weaken his own power, so he thought of sending an emissary, and in 109 BC, He He came to Goguryeo as an emissary.
At that time, after Wahe came to Korea, as an emissary, his important thing was to complete the tasks assigned by Emperor Wu of Han, but He did not complete the task, so when he returned to China, when a prince came to send him, but He directly killed him, and in order to ask for merit, he also said that the King of Joseon did not obey, so he killed him, at that time Emperor Wudi of Han listened to his words and also made him a high official. At that time, the Emperor of Joseon knew that after Wahe killed his men and was still enfeoffed, he immediately sent troops to kill Shōho, at this time Goguryeo had already taken the initiative to send troops, Emperor Wu of Han thought that there was no excuse to send troops to attack, and now he finally found a reason, so he took the opportunity to conquer Goguryeo.
In addition to this matter, at that time, the State of South Vietnam was also immediately subservient after the establishment of the Han Dynasty, but in 113 AD, Emperor Wu of Han found the same reason and sent troops to destroy the State of South Vietnam. Not only that, at that time, an emissary came to Dawan to buy some good horses, but at that time, good horses were the treasures of Dawanguo, which was difficult for them, and the emissaries of the Han Dynasty also touched the bottom line of dawan again and again, so the king of Dawanguo directly killed the han dynasty emissaries, and in the end, Dawanguo did not escape the fate of being conquered by the Han Dynasty, and finally Dawan became the breeding ground of the Han Dynasty.
In fact, at that time, it was not that these small countries liked war, and everyone knew that the Han Dynasty was a difficult country to mess with, and if they acted rashly, they would not have good fruit to eat. But everyone understands a sentence: Pifu is not guilty, with his guilt, in fact, when all the Han Dynasty emissaries go to every country, they are just a cover, this is just a fuse for Emperor Wu of Han to attack each country, after all, killing the emissaries may be an accident once or twice, if this kind of thing happens more, the clear-eyed people can see at once, this is just a routine of the Han Dynasty, and besides, as the most powerful Han Dynasty at that time, if you want to conquer a small country, you will not reason with them at all. It just needs a cover.