In the Tang Dynasty, Japan sent 15 envoys to China. Sending envoys is a publicly funded student from Japan sent to China to study Chinese culture and Buddhism. From the first dispatch in 630 AD to 894 AD (early Heian period), Japan sent a total of 15 batches of Tang envoys, each with a number ranging from 200 to 600. Some historians have calculated that an average of 400 people per batch sent 6,000 Tang envoys to China. However, there are only more than 3,000 people who have truly returned home.
Because during the Nara and Heian period in Japan, maritime navigation was extremely difficult and dangerous. People travelled on wooden boats without engines, but had to cross the sea. Dangers such as accidents, sinking and drifting can happen at any time. Sending Tang to return to Japan, only 8 times have been relatively smooth. In the end, almost half of the people were buried at the bottom of the sea or drifted away because of a marine accident.
The Chinese master Jianzhen and others were sent to Japan by the Chinese Tang Dynasty and experienced five failed voyages in 12 years. By the time they finally successfully set foot on Japanese soil, the master was blind.