Final answer:
Du Fu is accurately known as the "poet historian" because his poetry provides historical insights and documents significant events like the An Lushan Rebellion, reflecting the true impact on society and the environment of his time.
Step-by-step explanation:
Du Fu, a prominent poet of the Tang dynasty, is indeed referred to as the "poet historian." This is true because he chronicled events such as the An Lushan Rebellion through his poetry, reflecting his personal experiences and the impact of the turmoil on society. His works provide valuable historical insights into that period, documenting emotions and observations during times of significant upheaval. For instance, his poem "Springtime - Gazing into the Distance" poignantly captures the landscape of his broken country. Therefore, the contributions of Du Fu make him not only a great poet but also a valuable chronicler of his times, weaving history into his literary works.