What Historical event was Du Fu talking about in poem called (Gazing at Spring)

The poet Du Fu was talking about the invasion of An Lushan rebellion of 755.

Explanation:

Du Fu was a Chinese poet who wanted to a be civil servant but he lacked the required credentials to be a part of it. When the Au Lushan rebellion started he write to poetry. His torment continued for the next coming 15 years.

Au Lushan was considered as one of the most influential and powerful army general. The Tang dynasty was under his control. He is considered as one of the most barbarian leaders the Chinese tang dynasty has seen.