This study investigated the discussion process about preemptive attack to South Korea between North Korea and the Soviet Russia from 1949 till 1950, and found out the truth of North Korean initiative to the War.
After decisive division of Korean Peninsular North Korea made constant efforts to reunify Korea by the way of military action. But North Korea could not gain a victory over South Korea without Russia's support. Therefore he had to obtain Russia's agreement to war action to South Korea in order to gain Russia's support.
However at least 1949 Russia did not agree North Korea's intention to attack to South, because dispute between South and North could lead to Russia's undesirable intervention to Korean matter.
In the 1950 year Russia's perception to Korean issue altered fundamentally. In comparison with 1949 international environment changed to North Korean side. So Russia did agree North's intention to preemptive attack to South, and supported North's preparation of war. However this matter can not explain Russia's war initiative. Because at that time Russia did not participate to war actively and Russia's agreement to war was caused by North Korea's stubborn request.