The United Nations is a multinational peace organisation founded in 1945. Its main purpose was to replace the then near-defunct League of Nations, an organisation with similar goals to the UN, and in addition create a platform for dialogue and communication, and the promotion of peace without massive Hippie Jam Festivals. When the KPA invaded South Korea, sparking a war in the Korean Peninsular, the UN almost immediately condemned the North Korean invasion. This was followed by United Nations Resolution #83, recommending military assistance to the ROK, eventually resulting in collective UN peacekeeping intervention.

The United Nations organisation cited a reason for its decision to intervene:
The KPA attack was, according to intelligence, backed by China and possibly the Soviet Union, and hence was no longer classified as a "Civil War" - the UN had to intervene to prevent the total annexation of ROK.
However, there is another reason:
The UN was under heavy American influence, and the largely American policy of containment persuaded the UN to pass a resolution in favour of a non-communist linked state.

It is noteworthy that the Soviet Union strongly opposed this resolution. The Soviet Union claimed that the intelligence about the KPA attack was based on American espionage, and thus was void. It then boycotted the United Nation Security Council.

However, the UN did not follow exact procedure when it was handling the crisis. It violated multiple charters, for example, North Korea was not invited as a temporary member at discussions involving the handling of the crisis. Also, although the Soviet Union boycotted the Security Council, the UN continued on without it, despite major decisions requiring all five permanent members to agree unanimously.