Battle of Chosin Reservoir Korean War.
Fought in temperatures of around 35 below zero, the Marines were completely surrounded. The Army unit was pretty much wiped out, but in fairness had a lot of manpower with no training or experience(So Korean conscripts). The Army and Marines were on opposite sides of the reservoir.
The Marines were ordered North, to the reservoir up a mountain road. As they moved north, they came across Chinese troops which they were able to identify as a lot of the Marines had served in China during the late 1940s. Once they had an idea of what could happen, they left Battalions with supplies at strategic points along the road, as they knew they would have to fight their way out. Also, God Bless the US Navy and their air power.
https://www.wearethemighty.com/history/why-the-frozen-chosin-is-the-defining-battle-of-the-modern-marine-corpsQuote from the link
By the end of the battle, U.S. Marines suffered 836 dead and around 10,000 wounded. The Army had 2,000 dead and 1,000 wounded. The Chinese had the most catastrophic losses. Intelligence reported the Chinese as saying American forces could beat any Chinese effort, no matter the size.
Six Chinese divisions were completely wiped out. Of the ten that attacked, only one would ever see action again. Though the exact numbers are not clear, historians estimate Chinese losses anywhere from 30,000 to 80,000 killed. The numbers of Chinese wounded may never be known.