This study is to review the situation and importance of military defense facilities in Sacheon area, Gyeongnam Province, and punitive measures at late Goryeo and early Joseon Dynasty. Other points of this study are to review about the activities of Japanese invaded Sacheon in early Joseon Dynasty and to reassess the Sampo and Eulmyo Japanese Invasions in detail.
Having invaded into the Korean peninsula from primitive time, Wako mainly composed of Japanese expanded into a large scale group such as simultaneous attack with a fleet of 500 vessels.
A marine stronghold, and main key point, Sacheon has a site position vulnerable to Japanese private raiders' attack. However, there was no case that at late Goryeo and early Joseon Dynasty, Wako's attack was concentrated. The reason was that the neighboring area, Happo(Masan) was a military and administrative center, so subject to preemptive attack, and Sacheon subject to subsidiary attack.
Also it was also understood to be due to natural geographic factor that attacking Sacheon needs to conquer Yogjido, Sangdo, Hado and the South sea in advance.
Literary records showed that Sacheon was never subject to independent attack, but same attack along with adjacent areas like Geoje, Goseong and Happo.
The reason why Sacheon was relatively little damaged by Wako was found to have been derived from military, administrative, natural and geographical factor.