I think it was the Tang Dynasty. The following is an analysis.
At the beginning of the Western Han Dynasty, China was attacked and invaded by Xiongnu, so he couldn't lift his head. Every year, he paid tribute to a nomadic people and even was forced to kiss them. It can be seen that the Central Plains of China was not very strong in the early Western Han Dynasty, and this situation continued until the period of Emperor Wu of the Han Dynasty. By the middle of the Western Han Dynasty, China began to prosper, its foreign trade improved, and its military strength greatly increased. Technology was also ahead of the society at that time.
Let's talk about the Tang Dynasty, Emperor Taizong, Wu Zetian and Xuanzong Kaiyuan years. This is the most prosperous period of China's ancient feudal society. At that time, the system, science and technology, army and politics were the most perfect, leading and powerful in the world. This is also recognized by historians as the most prosperous period of China's ancient feudal society.
China was even called "the prince of heaven" by Li Shimin. At that time, China's status was even higher than that of the United States now.