Quite right DT,
I've had a relative (brother of my great grandfather) who went into resistance here in Belgium, derailing trains and such. But early on already he was caught by the germans and ended up in a prison camp. He stayed there for a while, making a friend with very pronounced communist ideas. Together they decided to organise their escape, and since Russia was closer to the camp (or easier to get to, I don't know too much details) + influence from the friend they both decided to flee to the russians. And they succeeded too. Once arrived, they got 'caught' by the soviets. And even though they couldn't speak a single word russian, their ability to read a map and their experience in enemy territory made that both of them got promoted officer, each commanding a handful of men. They didn't have much choice, go fight for them or end up in a gulag.
So they spent the largest amount of time, almost 3 years, in the war at the russian front. My uncle never said anything about his experiences there, I think it would've been too painful for him. All we know is he lost his friend there, who was searching the german bodies for valuables and got shot while at it by a wounded german.
At the end of the war both allied armies, americans/british/canadians... met in Berlin, but had an agreement that both would send eventual deserters back to their army. My uncle deserted to the americans anyway. The american officer in charge of him phoned his relatives to check his story, but there they all said my uncle was dead (since they hadn't heard of him in several years). My uncle heard that, and had to shout to the phone for his family to recognise his voice.
A bit less luck and he would have had to stay in communist Russia for the rest of his life...