Complex sentence: Meantime, Chen Shi had been losing control of upstream Yangtze to Sun Quan's generals, Song Qian and Zhu Ran, and the naval commander fled into Ma'an Hills to rendezvous with the remnants of Liu Bei's once-refulgent army.
Split into simpler sentences: Meantime, Chen Shi had been losing control of upstream Yangtze to Sun Quan's officers Song Qian and Zhu Ran. He fled into Ma'an Hills to rendezvous with the remnants of Liu Bei's once-refulgent army.