Why did they need to prepare, practice, and fight?
Firstly, they were afraid that if peace lasted for too long, the bloodlust of a soldier would disappear. They would think that they were a real soldier after going to the training ground. Secondly, they needed to innovate and improve constantly. They needed to discover new problems and improve their combat ability continuously.
As the saying goes, 'If you want to fight, you will die. If you don't fight, you will be in danger.' If you don't fight, you won't practice. If you don't use your soldiers to fight, you will only guard your own field every day. Those were all just for show. If someone else fired a shot, they would be wiped out.
Soldiers were the guardian deities of a country. If even their guardian deities became weak, the country would be destroyed.
