Goguryeo met major setbacks and defeats during the reign of Gogukwon in the 4th century. In the early 4th century, the nomadic proto-Mongol Xianbei people occupied northern China. During the winter of 342, the Xianbei of Former Yan, ruled by the Murong clan, attacked and destroyed Goguryeo's capital, Hwando, capturing 50,000 Goguryeo men and women to use as slave labor in addition to taking the queen mother and queen prisoner, and forced King Gogukwon to flee for a while. The Xianbei also devastated Buyeo in 346, accelerating Buyeo migration to the Korean peninsula.