I spent 20 years working in WY. ND. and MT. working as surveyor throughout the winter.
Bobstoy is right - when you are driving in un-tracked snow, you often run over a unseen depression in the terrain your your frame is suspended on snow and your wheels are dangling with no traction what-so-ever. And I used have chains on all four wheels most days when off-road.
I this situation, I needed a multi-mount winch that I could mount to the front or the rear and "Pull-Pal" winch anchor which drives itself through the snow and into the ground and gives you something to anchor to. In the prairie, there ain't no trees...
One time my Pull-Pal snapped off and I was seriously stuck. I spent 6 hours digging and digging under the frame puling snow out. I finally got the wheels to touch traction and drove straight back on my track to a good road. I couldn't contiune without that winch / anchor set-up.
Be careful! Always have food, sleeping bag and a way to stay warm in case you have spent the night in your truck and walk out the next day.