Chang' an fell, the country was broken, and only the mountains and rivers remained; Spring has come, and the sparsely populated Chang' an city is densely forested. What historical events did "Bao Guo" write? Which city does "city" refer to? "national destruction" refers to the Anshi rebellion. "City" Chang 'an City.

From Tang Suzong to Deyuanzai (756), in June, An Shi Rebellion captured Chang 'an, Tang Dou. In July, Du Fu heard the news of Tang Suzong's accession to the throne in Lingwu, and made his home in Qiang Village, Zhangzhou, and went to Su Zong. On the way, he was captured by rebels and taken to Chang 'an. He was not imprisoned because of his humble position. Hope in Spring was written in March of the following year. The poet witnessed Chang 'an's flute falling and homesickness in adversity, and he couldn't help feeling deeply.