At the time of Gwanggaeto's birth, Goguryeo was not as powerful as it once had been. In 371, three years prior to Gwanggaeto's birth, the rival Korean kingdom of Baekje, under the great leadership of Geunchogo, soundly defeated Goguryeo, slaying the monarch Gogukwon and sacking Pyongyang. Baekje became one of the dominant powers in East Asia. Baekje's influence was not limited to the Korean peninsula, but extended across the sea to Liaoxi and Shandong in China, taking advantage of the weakened state of Former Qin, and Kyushu in the Japanese archipelago. Goguryeo was inclined to avoid conflicts with its ominous neighbor, while cultivating constructive relations with the Former Qin, the Xianbei, and the Rouran, in order to defend itself from future invasions and to bide time to reshape its legal structure and to initiate military reforms.