China was so powerful in ancient times, why didn't it invade other countries?

This question is actually not rigorous! We see that all countries in Southeast Asia are subordinate to or dependent on China, and aggression here can be understood as occupation or territorial expansion! Historically, Viet Nam, Myanmar, Laos, North Korea and so on are all part of China culture! There are several reasons why China has not expanded beyond Asia. 1, geopolitics, China is located in East Asia, with a vast territory and rich resources, bordering the sea in the east and inland in the west. Whether in the north or the west, the environment is relatively bad, the region can meet most of the needs, and the material is also very rich! 2, cultural influence, more than 2000 years of mixed culture of Confucianism, Buddhism and Taoism will make China people form a polite country! Don't argue, don't rob, like to convince people by reasoning! People with peaceful nature! 3. The attitude of the rulers, except for the wanton expansion of the Yuan Dynasty, was relatively normal in other dynasties in history. Once they are invaded, they will face death and economic conditions. More importantly, they will not be well managed and will eventually fall apart, which is not worth it! The purpose of aggression is to obtain better resources and transfer some local contradictions, but ancient China did not meet the requirements on these two points!