Sounds like a great book Fish.
I had thought it might be this one: "The Long Walk Home with Miracles Along the Way" By Anatole Kurdsjuk but after reading a preview in google books maybe not.
Then there's this one which was originally published in 1955 that might be it:
"As Far as My Feet Will Carry Me" By Josef Martin Bauer
Reminiscent of S_avomir Rawicz's classic The Long Walk, an amazing narrative of escape and survival.
In 1944, German paratrooper Clemens Forell was captured by the Soviets and sentenced to twenty-five years of labor in a Siberian lead mine. In the Gulags, this was virtually a death sentence. Driven to desperation by the brutality of the prison camp, he staged a daring escape. For the next three years, Forell traveled 8,000 miles in barren, frozen wilderness, haunted by blizzards, wolves, criminals, the KGB, and the fear of recapture and retribution. Only a remarkable will to survive, and a bit of luck, allowed him to reach the safety of the Persian border. The resulting story is a rare document of the horrors faced by POWs in the Soviet Union, and a testament to the human spirit.
Here's another link to read about this book...
Google preview of "As Far as My Feet Will Carry Me" By Josef Martin Bauer, Clemens Forell