Construction Techniques and Significance of the Hagosŏngja Fortress of Koguryŏ

This study examines the fortress structure and construction techniques of Hagosŏngja Fortress, located in Hwanin, Liaoning Province, China, with the aim of identifying its key characteristics and historical significance through comparison with other earthen fortresses from the Koguryŏ and Han periods in Northeast China. Previous interpretations have suggested either Han influence or Koguryŏ origin in its construction; however, stratigraphic investigations and comparative analysis do not support these claims. The ramparts of Hagosŏngja Fortress were not built using alternating fill (Kyohosŏngt'o) or rammed earth techniques (P'anch'uk), but rather through a general method of horizontal layering. Notably, the structure exhibits a distinctive feature wherein the core and inner/outer walls were constructed simultaneously, interlocked in a staggered fashion. This technique is clearly distinct from the segmented construction method found in Han-period fortresses and instead shows strong structural affinities with the wall construction of the Dongtuanshan of Puyŏ and the Sŏgo Fortress of Balhae. These findings suggest that Hagosŏngja Fortress should be understood not as a derivative of Han fortress models, but rather within the broader architectural tradition of ancient Northeast Asian states. As one of the earliest known earthen fortresses of Koguryŏ, its construction illustrates the technological and cultural continuity that links Puyŏ and Balhae. While limitations remain due to partial wall collapse and gaps in excavation data, further archaeological investigation is expected to offer deeper insight into the development of construction methods at Hagosŏngja Fortress and its relationship with surrounding regions.