This paper reexamines the limitations of the Japanese invasion of Korea and the defensive capabilities of the Chosŏn armies by emphasizing the strategic significance of the Naktong River, the formation of the Pusan-P’yŏngyang great front, and the power imbalance between Japanese forces in the northern and southern regions of the Sobaek Mountains. During the first two months of the war, the Chosŏn military observed the disparity in Japanese strength between these regions and recognized the military value of western Kyŏngsang, a vital area linking the Korean Strait to central and western Korea via the Naktong River. In response, the Chosŏn armies implemented a confrontational strategy throughout the latter half of 1592, utilizing proactive and preemptive tactics to impede Japanese advances in both northern and southern western Kyŏngsang. The expansion of the front line within western Kyongsang as above exposed concurrent battlefields on both sides of the Sobaek Mountains, endangering not only the Japanese occupation of western Kyŏngsang but the entire Kyŏngsang province, the initial point of invasion. This paper explores the resilience of the Chosŏn armies' defense, focusing not only on its enhanced combat performance but also on its broader strategic impact, encompassing the Korean Strait, Naktong River and western Kyŏngsang. By doing so, it highlights the strategic weaknesses of the Japanese armies evident from the early stages of the war, even before the massive Ming intervention and the restoration of P’yŏngyang in January 1593. The Chosŏn armies' geostrategic foresight and determined execution in western Kyŏngsang enable us to reassess its role as a central war actor and have a deeper understanding of the Imjin War as an international conflict between Chosŏn, Ming, and Japan in the late sixteenth century.