The adoption of United Nations Security Council Resolution 90 was a crucial moment in international military and diplomatic engagement during the Korean War. Through this resolution, the Security Council aimed to bolster South Korea's defense against the advancing North Korean forces, which had invaded the South in June of the previous year. The council condemned North Korea's actions as a violation of international peace and security. Resolution 90 not only called for the immediate cessation of hostilities but also requested that UN member states contribute military support to South Korea to help repel the aggression and restore peace in the region.

Following the invasion, the UN had already taken several steps to assist South Korea. The Security Council had previously authorized military action through Resolution 83, which culminated in the establishment of a UN Command to oversee military efforts in the conflict. Resolution 90 reaffirmed this commitment by specifically advocating for a coordinated response and emphasizing the importance of international cooperation to address acts of aggression. The resolution underscored the growing role of the UN in global security and military interventions, setting a precedent for future actions by the organization in conflict zones.

The backdrop of the Cold War heavily influenced the discussions leading to Resolution 90. The United States and its allies were concerned about the spread of communism in Asia, while the Soviet Union supported North Korea. The resolution is notable not only for its political and military implications but also for its demonstration of collective security principles under the UN Charter. Ultimately, Resolution 90 served as a significant point in the overarching narrative of the Korean War, solidifying UN involvement and aligning member states' military efforts against North Korean aggression.