I want to know the answer to the following question:
What tactics of the PVA were US and ROK troops not prepared to handle?
All the background I'm provided with is that "On 27 November at the Korean eastern front, a U.S. 7th Infantry Division Regimental Combat Team (3,000 soldiers) and the U.S. 1st Marine Division (12,000–15,000 marines) were unprepared for the PVA 9th Army Group's three-pronged encirclement tactics at the Battle of Chosin Reservoir, but they managed to escape under Air Force and X Corps support fire—albeit with some 15,000 collective casualties.". Is that enough to answer the question?
Answer: yes