Why did the temporary division of Korea become permanent after 1945?

The temporary division of Korea along the 38th parallel was initially established in 1945 as a military expedient to facilitate the surrender of Japanese forces to the United States and the Soviet Union. However, this division became permanent due to the intensifying Cold War and the failure of diplomatic efforts to reunify the peninsula.123

Attempts to establish a unified government through a Joint U.S.-U.S.S.R. Commission foundered in 1946 and 1947 because the two powers could not agree on which Korean political groups to consult. When the United States brought the issue to the United Nations, the Soviet Union barred the UN commission from the northern zone. Consequently, separate states were formed in 1948: the Republic of Korea in the south and the Democratic People’s Republic of Korea in the north. Each government claimed sole legitimacy, and the division was further hardened by the Korean War, which ended in a ceasefire rather than a peace treaty, leaving the peninsula technically at war.32