1. Suwu Shepherd. It is said that Su Wu was detained by Xiongnu when he went to Xiongnu, and he would rather die than surrender. Exile of herding sheep in Beihai lasted 19 years. Khan was lured to surrender many times, and his good friend Li Ling advised him to surrender, but he remained unmoved.

2. It can't be Korean. 19, the Huns made up with the Han Dynasty, but the Huns lied that Su Wu was dead and refused to return Su Wu, so Su Wu missed several opportunities to return and never went back.

3. Hongyan passed the book. When China's envoy arrived again, one of Su Wu's men quietly met China's envoy and said that Su Wu was still there. When Ambassador China saw Khan, he said that Emperor Wu of the Han Dynasty had hunted a wild goose with letters tied to it, saying that Su Wu was still alive. Khan has no choice but to make friends.

In fact, as early as the pre-Qin period, due to the seasonal migration of Hongyan, it was as regular as a messenger, which made people sprout the idea of Hongyan passing books. But this is unrealistic, because Hongyan, as a wild animal, will not do what people want. In ancient times, only homing pigeons were real ambassadors.