I would agree with everything Ross and Tom said; and add a few things. In addition to dry socks, change into a dry shirt, and if you can drawers. The more you have on thats dry, the warmer you will sleep. You can also heat a rock, and keep your feet on it inside your blankets. Eat before you sleep. The calories your burning will keep you warm. Visit the sinks before bed. Insulate, layer, and keep your head and feet warm and dry.
Remember the acronym COLD
keep your clothes Clean, avoid Overheating, Layer your clothing, and keep it Dry. You can also pair up with a pard, and share blankets and ground clothes (one over and one under) and body heat,
I learned alot about keeping warm while serving with the 6th Inf Div (Light) in Alaska. Most of our ops were in the winter, so we learned fast. We learned how to sleep in a hooch in the snow without heat sources, and most of what I mentioned is from that experiance
Good luck.... aint no reason to be freezin'.. and if your in the infantry.. travel light, freeze at night!
Co A, 2nd Battalion Ga Sharpshooters/64th Illinois Vol Infantry "Yates' Sharpshooters"
Savannah Republican Blues
Co C, 3rd US Infantry
Ships of the Sea Maritime Museum & William Scarbrough House, Savannah, GA
"I hope to live long enough to see my surviving comrades march side by side with the Union veterans along Pennsylvania Avenue, and then I will die happy." - James Longstreet at a Memorial Day Parade in 1902.