The origins of the Korean War: Civil war or Stalin's Rollback?

This essay seeks to evaluate civil war theories on the origins of the Korean War by distinguishing between the permissive and efficient causes of war. These theories explain the causes of the war in terms of an extension of border clashes. To explain the efficient cause, Bruce Cumings advances the controversial 'second mosaic' thesis which argues that the war was sparked by the South's provocative actions on the Ongjin peninsula, and quickly spread to the thirty-eighth parallel with the mobilization of Northern troops. Yet new Soviet archival materials enable us to develop the hypothesis of the second mosaic in reverse since Kim Il Sung proposed the Ongjin occupation plan to Stalin. In testing Cumings's 'second mosaic' and the reversed second mosaic thesis, this article sees the origins of the war in Stalin's rollback strategy whose essence was using North Korean troops to cross the US containment line and displace the territories under the US sphere of influence for the first time since the inception of the Cold War.