Even before the two government of Korea peninsula were deputed officially, north Korea began organizing the military and solidifying such as establishing a peoples republic to communize entire Korean peninsula by force with democratic base theory. On the other hand, South Korea had not have effective progress of the effort to establish a military and solidify, because of the political confusion of the early stage of the founding of the country, poor economic situation, negative attitude of American and leftist power & maneuvers. While North Korea was preparing for a force unification, Archison, the State Minister of America, announced the 'Archison line' which is the announcement of taking Korea Peninsula out of American's protection, in 12th Jan 1950.

This even more exited the northern Korean to invade the south by military force. On 25th June 1950, around 4:00 in the morning, north Korea made sudden attack through whole region of 38line starting the fratricidal war tragedy of 3years and the north Korean solders occupied Seoul in 3days and continued attacking toward South U.N organized the security committee in 27th June 1950 and regulated the invasion of south by North Korea as the "Destruction Act. of peace", the violation of U.N charter and ordered to stop the hostile action and withdraw back to north of 38lin. If these orders are not made, they will inflict declaration of military sanction to maintain the world peace and security.

But such declaration was ignored and war was continued. UN therefore organized UN force of America and 15 other countries and this UN force allied with Korean army and advanced up to Abrog River at Oct. same year. But after the end of Oct, more than 1million the Communist Chinese Army started to get involved making the 6.25 war more international among the continuous war of attrition of two and half years, in 10th June 1951, the partial cease-fire negotiation and reach a cease-fire agreement on 27th starting the cease-fire. With this Korea had not cleared the division in spite of the incredible scarifies of 6.25 war; the only difference was that 38 line has now changed to cease-fire line rather than demarcation line. As a result, two Koreas follow the different path of the development maintaining the perfect opposing relationship.