The ancient government controlled salt, mainly because the price of ancient salt was very high, and it was also an essential seasoning for the people. People can eat no other spices, but they must eat salt. If you don't eat salt for a long time, you will feel weak and basically lose your ability to work. In ancient times, people mostly engaged in heavy manual labor, so the demand for salt was very important. When the government has mastered salt, it can have a considerable and stable tax revenue, and even in some cases, salt tax can even account for half of the national tax revenue, which is very important to the country.

Secondly, due to the poor technology of extracting salt in ancient times, ordinary people can't make salt by themselves. If they want to make salt, they must have a large-scale saltworks. As long as the state controls these salt fields, ordinary people can only buy salt at high prices, which is relatively easy to control.

Finally, the ancient countries vigorously controlled salt, or for military and political considerations. Because there were wars in ancient times, from peasant uprisings to bandit uprisings. And salt is a necessity for human survival and combat. Without salt for a long time, people can't even do work, let alone fight. The origin of salt is in some specific coastal areas. As long as the state controls salt and curbs salt roads, the other side can't beat the state without salt.

This practice is generally not used for internal counter-insurgency, because once the country breaks the salt channel in a certain area, not only the rebels or the armed forces that need counter-insurgency lose their combat effectiveness, but also the ordinary people lose their ability to live and work. This is an extremely despicable means of fighting and very unpopular. However, during the Japanese invasion of China, the Japanese occupation army curbed the salt channels in the liberated areas in this way, which made the life of the soldiers and civilians in the liberated areas very difficult. But we survived the difficult period with wisdom and perseverance, and finally won the national liberation.