Ko Sŏnji 高仙芝, a prominent Tang dynasty general of Koguryŏ 高句驪 descent, led extensive military campaigns against nomadic groups along China’s northwestern frontiers, extending imperial influence deep into Central Asia. Despite his remarkable early successes, his life ended in tragedy with a brutal execution under questionable charges of embezzlement and corruption, orchestrated by a court eunuch. Ko’s legacy remains contested; some scholars attribute the Tang dynasty’s declining presence in Central Asia to his defeat at the Battle of Talas in 751—a pivotal moment that marked China’s withdrawal from the Silk Road amid the advance of Islamic power. This event signaled a shift in Tang foreign policy from expansion to defense, weakening China’s strategic and commercial position on the Silk Road. This paper reevaluates Ko Sŏnji’s significance in Chinese history and Sino-Central Asian relations through three key lenses. First, it considers how his non-Chinese background influenced his rise and vulnerability within the Tang court. Second, it examines the trajectory of his military career, focusing on the circumstances of his defeat at Talas and its possible connection to his downfall. Finally, it assesses the broader historical implications of the Battle of Talas for Tang China’s engagement with Central Asia and the Islamic world. In reassessing Ko’s life and career, this study sheds new light on the complexities of military expansion, frontier management, and transregional interaction in the seventh and eighth centuries.