S3: What factors made Korea vulnerable and appealing for military occupation? What geopolitical factors in the 20th century led Korea’s invasion and occupation in June 1950?

As the Second World War came to a conclusion and the bipolar balance of power began to emerge, it became clear to American military leadership that the Korean peninsula was a prize that could not be surrendered to the quickly advancing Soviet forces. Though some other comments here note the natural resource wealth of Manchuria and Korea as a major contributing factor, I would posit that the driving factor in the conflict was instead the geostrategic importance of the Korean peninsula. Given the deficiency of human and industrial capital in both Manchuria and Korea in 1950, it is apparent that the conflict was not about access to Korean resources, but rather about the geographic significance of the peninsula in greater Northeast Asia

Since ancient times, the Korean peninsula has served as a geographic fulcrum of power for great military powers from the Mongol Khans to the Japanese Empire. Extending south into the Sea of Japan, the peninsula is a figurative sword of Damocles hanging over the Japanese Archipelago, offering mainland powers a convenient logistical base for excursions into Japanese territory. Simultaneously, the rough coastlines and mountainous terrain offer those who control the peninsula a shielded land-power foothold in northeastern Asia, granting overland access to the mountains of Manchuria and the Siberian interior. Most importantly, however, control of the peninsula nearly assures regional naval hegemony in the greater Yellow Sea, offering convenient military access to coastal Chinese population centers.

Wisely recognizing the palpable threat that a Soviet or Sino-controlled Korea would pose to American influence in Japan and ultimately the whole of Asia, American military planners quickly moved to counter the Soviet threat. The occupation of Korea by both American and Soviet forces was far more than simply vulnerable and appealing; both powers recognized that occupation was absolutely necessary in order to maintain their respective regional influence. With the division of the peninsula and the subsequent military buildup along both sides of the temporary border, an impending military conflict was all but inevitable.