What is the reason for the poem "General's white hair cries for his husband"?

This is an ancient poem that exposes the war. The people long for peace, and the people want happiness. There are generally two reasons why they don't fight: 1, "and Emperor Wu's heart is still beating for the war". The emperor likes to fight in order to win more territory. 2, social unrest, people living in poverty, wars everywhere, some local governments try to rebel or the country is restless, foreign enemies invade ~ ~