alternatehistory.com

In march 1950 the UN passed Resolution 82, to aid South Korea from unlawful invasion. They managed this because of a Soviet boycott over Taiwan having China's seat on the Security Council, hence USSR did not use its veto. However the Russians no doubt knew about the invasion, the CIA did. It seems they had interpreted UN bylaws wrong, believing the absence of a SC member would deadlock any deal, much like an active veto. Arguably they hoped such a route would be more subtle than retaking their seat in time to help their comrades.

However lets say the Soviets do resit in time for Resolution 82 and veto it. They did have some legal (if pedantic) reasons to hold it up, namely North Korea's lack of representation and UN laws stating that technically the invasion was a civil war, so not an illegal invasion of a sovereign state.

I'm pretty sure the US and others would still want to jump to South Korea's aid but with a bogdown discussion in the UN would in come in time, the UN relief forces literally arrived as the South Koreans were falling into the sea.
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