8세기 후반 唐-吐蕃 관계와 그 주변 정세 ― 위구르・南詔・아바스 조・天竺에 대한 협공 요청을 중심으로 ―

Abstract

This study investigates the diplomatic transformation between the Tang dynasty and the Tibetan Empire(Tubo) in the late 8th century, focusing on how the Tang court sought to manage its deteriorating position through multilateral diplomatic strategies. Following the An-Lushan Rebellion(755–763), the Tang state was significantly weakened both militarily and fiscally, while Tubo reached the height of its territorial expansion under the reign of Khri srong-lde brtsan. During this period, Tubo not only occupied crucial territories in Gansu and Qinghai but also temporarily seized the Tang capital of Chang’an in 763. Tang-Tubo relations fluctuated between fragile truces and sudden hostilities, culminating in the so-called “Peace Treaty of Qingshui”(783) and the disastrous “P’ing-liang Ambush”(787), in which the Tang envoy Hun Jian narrowly escaped capture during what was presented as a formal alliance renewal. These events reflect a critical phase in Tang foreign policy, wherein traditional tributary frameworks were rendered ineffective and more pragmatic, horizontally-structured diplomacy became necessary. In the aftermath of the failed negotiations with Tubo, Emperor Dezong of Tang attempted to orchestrate a regional containment strategy by appealing to Tubo’s rival powers—including the Uighurs, Nanzhao, the Abbasid Caliphate(Dashi), and India(Tianzhu)—for a coordinated military and diplomatic response. This paper examines the motives and feasibility of such appeals by closely analyzing both Chinese and Tibetan sources, including official chronicles(Jiu Tangshu, Xin Tangshu, Zizhi Tongjian), early Tibetan inscriptions such as the Zhol Pillar, and Dunhuang manuscripts(e.g., Old Tibetan Annals and Old Tibetan Chronicle). Special attention is paid to the discrepancies in narrative between Tang-centric records and Tibetan documentation, which suggest differing perceptions of legitimacy, hierarchy, and alliance. Rather than viewing the Tang court's coalition-building efforts merely as effective diplomacy, this paper explores the extent to which these appeals were grounded in concrete geopolitical calculations. By analyzing the internal and external circumstances of each invited state, this study argues that the Tang court's outreach efforts—particularly to the Uighurs, Nanzhao, the Abbasids, and India—were not merely rhetorical but reflected real possibilities for coordinated opposition to Tubo. In the case of the Abbasids and India, this paper draws on both Tang records and non-Chinese sources, including al-Ṭabarī’s chronicle, to suggest that these polities had independent strategic motivations for engaging with Tang China. While the documentation remains limited, the existence of shared interests—especially in curbing Tibetan influence in Central Asia—renders such diplomatic responses historically plausible. Ultimately, this research situates late 8th-century Tang-Tubo relations within a broader East and Inner Asian diplomatic context, challenging Sino-centric historiography and emphasizing the fragmented, multipolar nature of regional power dynamics during this transitional period in Asian history.