His reign ended when Baekje was conquered by an alliance of the rival Korean kingdom Silla and China's Tang dynasty.
During this time, the northern Korean kingdom of Goguryeo, under the control of Yeon Gaesomun, took aggressive stances against Silla and the Tang.
According to a legend in the Samguk yusa, Mu was a Baekje peasant who married Princess Seonhwa of Silla (making her Uija's mother), but this is not considered orthodox history.
Sabi, Baekje's capital, (in present-day Buyeo, South Chungcheong Province) was surrounded by the Silla-Tang allied forces.
Uija and the crown prince escaped to Ungjin (in present-day Gongju), but surrendered when Sabi fell.