His poems reflect the historical process from prosperity to decline in the Tang Dynasty. What's it called?

Du Fu (7 12-770) was born in Gongxian County (now Gongyi, Henan Province). Du Fu's great-grandfather (Du Fu's father) moved from Xiangyang (now Hubei) to Gongxian (now Gongyi, Henan). He was a great realistic poet in the prosperous Tang Dynasty. He is concerned about the country and the people and has a noble personality. Later generations called him "the sage of poetry", and his poems were also called "the history of poetry". Du Fu and Li Bai are called "Du Li". In order to distinguish it from the other two poets, Li Shangyin and Du Mu, namely "Little Du Li", Du Fu and Li Bai are also called "Big Du Li".