Gija Joseon was purportedly founded in the 12th century BC, but its existence and role have been controversial in the modern era. Three of the commanderies fell or retreated westward within a few decades. As Lelang commandery was destroyed and rebuilt around this time, the place gradually moved toward Liaodong. Goguryeo, the largest and most powerful among them, was a highly militaristic state,   and competed with various Chinese dynasties during its years of history. Goguryeo experienced a golden age under Gwanggaeto the Great and his son Jangsu ,     who both subdued Baekje and Silla during their times, achieving a brief unification of the Three Kingdoms of Korea and becoming the most dominant power on the Korean Peninsula. Balhae was founded by a Goguryeo general and formed as a successor state to Goguryeo.