Tell me about your in-depth understanding of "Iron-made Camp and Flowing Soldiers"

The iron camp and the flowing water of the soldiers mean that the barracks are fixed, and every year the old soldiers leave and the new soldiers come, it is like flowing water. This is how the soldiers who built the iron-clad camp and had flowing water came from. He also said that the barracks are fixed and the soldiers are mobile. This illustrates the hard work of those who serve as soldiers.

This sentence usually appears when parting. The iron camp refers to the fixed barracks and living facilities. They will never change. Those who serve in the army are required to perform military service. There is a certain time limit when the metropolis retires and returns to his hometown. This departure is like running water, and the only thing that remains unchanged is that the clanking barracks are still standing. At first, this sentence simply meant a phenomenon in the army, and later it was extended to Leave separately. For example, students graduate, soldiers retire, etc.