Sorry if this is a bad sub for this question. He started talking and my mom had told me he NEVER talked about his experiences so I didn't want to interrupt to clarify much.
So he was in the Army during Korea. I learned I was going there soon to Osan so we talked about that for a minute and he asked where that was. He thought he had landed there but then remembered it was itsan (insan, it sounded like that). At that time they controlled that beach so not fighting there then he moved into chugan (chucan) valley where there was fighting going on. This was during the winter because he was talking about how dang cold it was.
I googled what I thought I heard him say but it didn't give me any hits. Hoping someone might be able to help me out based on what I heard. Thank you for any help, even if you point me somewhere else!
Could it have been Inchon (now spelled Incheon)? Major battle there. Another place for a major battle was Pusan (now called Busan).
From the description he most likely landed at Inchon, which was the major counterattack that introduced much larger amounts of US forces on to the Korean Peninsula and effectively cut North Korean supply lines leading to their retreat and allowing the US to force them up to the Yalu River before Chinese involvement reversed the offensive and led to stalemate around the 38th Parallel.
The second location he mentions could be the Chosin Resorvoir (also known by its Japanese name Changjin, which is a bit closer to what you heard) which is where the US offensive stalled out. It took place 3 months after Inchon and marked the first major Chinese involvement. Chinese troops were able to surround US forces and inflict heavy casualties over a two week period before the US forces regrouped and retreated to the 38th parallel.
There are several excellent histories of the Korean War that are very readable. Mathew Ridgway, the commander who took over the 8th Army after the disaster at Chosin and later took over for MacArthur, wrote one called The Korean War, T.R. Ferhenbach's This Kind of War is a classic, if you want a more academic history William Steuck wrote a couple good ones on the conflict that take into account the opening of Soviet archives.