Analysis of information sources in references of the Wikipedia article "Former Yan" in English language version.
Soon after, the Wei fell to the Jin and Koguryŏ grew stronger, until in 313 they finally succeeded in occupying Lelang and bringing to an end the 400 years of China's presence in the peninsula, a period sufficient to ensure that for the next 1,500 it would remain firmly within the sphere of its culture. After the fall of the Jin in 316, the proto-Mongol Xianbei occupied the North of China, of which the Murong clan took the Shandong area, moved up to the Liao, and in 341 sacked and burned the Koguryŏ capital at Hwando. They took away some thousands of prisoners to provide cheap labour to build more walls of their own, and in 346 went on to wreak even greater destruction on Puyŏ, hastening what seems to have been a continuing migration of its people into the north-eastern area of the peninsula, but Koguryŏ, though temporarily weakened, would soon rebuild its walls and continue to expand.
