Question: Which event took place first, Operation Undertone or The Battle of the Ch'ongch'on River?
Sentence (from "Battle of the Ch'ongch'on River"): The Battle of the Ch'ongch'on River, also known as the Battle of the Ch'ongch'on () or the Second Phase Campaign Western Sector (), was a decisive battle in the Korean War, and it took place from November 25 to December 2, 1950, along the Ch'ongch'on River Valley in the northwestern part of North Korea.
Relevant evidence: Yes