The Silla–Tang War occurred between the Korean Silla kingdom with the remnant forces from Goguryeo and Baekje, and the Chinese Tang empire. It began in the geopolitical context immediately following the conquest of Goguryeo and Baekje by Silla and Tang. The conflict ended with a truce between Tang and Silla due to the internal political situation in both states, with the dividing territorial line at the Taedong River basin.
Context
The Silla–Tang alliance, which had defeated both the Korean kingdoms of Baekje and Goguryeo, resulted in the occupation of the former territories of both of these kingdoms by coalition armies. After the fall of Goguryeo in 668 AD, the Tang Emperor created the office of Protectorate General to Pacify the East and attempted to place the entireKorean Peninsula, including its erstwhile independent ally Silla, under its rule. The Silla-Tang alliance subsequently fell apart as the Tang tried to establish dominion over the Korean Peninsula through this new office and its former ally Silla resisted these efforts. King Munmu of Silla assembled the Silla army with the armies of the defeated kingdoms Goguryeo and Baekje in a coalition against the Tang army.. He had the unenviable challenge of freeing his country and hard-won conquests from Tang domination. To achieve this, Munmu forged alliances with Goguryeo resistance leaders such as Geom Mojam and Anseung, and launched attacks on the Tang forces occupying territories formerly belonging to the conquered kingdoms of Baekje and Goguryeo. Starting almost immediately after the fall of Goguryeo in 668 AD and the establishment of the office of Protectorate General to Pacify the East, the struggle between the former allies lasted through much of the 670s AD.
Course
By 674, Tang and Silla were in frequent battle, as King Munmu had taken over much of the former territories of Baekje and Goguryeo from the Tang forces that had occupied these lands following the Goguryeo–Tang War and Baekje–Tang War, and fostered native resistance against the Tang in those territories of the other Korean kingdoms still occupied by the Tang. In this year, Emperor Gaozong, in anger, arbitrarily declared King Munmu's brother Kim Inmun to be the king of Silla and commissioned Liu Rengui with an army to attack Silla. However, before any major battles could be fought, King Munmu, for unknown reasons, formally apologized and offered tribute; this satisfied Emperor Gaozong, and, not wanting to prolong the campaign, he ordered a withdrawal and recalled Kim Inmun. In 675, Li Jinxing reached Sillan territory via land, using Mohe forces in Manchuria that had submitted to Tang, with the intent of occupying territory in Silla. However, the Tang forces were defeated by a Sillan army at the Maeso fortress, in or near present-day Yeoncheon. In 676, Xue Rengui crossed the Yellow Sea to fight against Silla.
Aftermath
Afterwards in 676, the Tang government moved the Protectorate General to Pacify the East to Liaodong. Although the Tang forces lost the conquered territories south of Taedong River, Silla could not regain the former Goguryeo territories to the north of Taedong River, which had fallen into Tang dominion. The Tang empire had taken control of Liaodong Peninsula, while Silla controlled the Korean Peninsula. Relations between Tang and Silla ceased until the early 8th century, when King Seongdeok of Silla and Emperor Xuanzong of Tang reestablished diplomatic ties and initiated a reconciliation between the states.
