Follow up: If there were people that did this and were caught, what would the punishment be?

Follow up: How plausible would it have been for an American to do this, during the Korean War, a la Don Draper from Mad Men?

Kathrine Hulme mentions in "The Wild Place" that they had Russians pretending to be Poles in the displaced persons camps. They were able to get DP papers because

a) there had been ethnic Russians in the old borders of Poland, so it was a bit easier to blend in, and there were similarities of language

b) with the Soviet occupation of Poland, there was no way to check to see if they were who they claimed to be, &

c) those few Russians in the camps got along well with the Poles, and so the Poles covered for them.

From this, 1) you had to be plausible for that ethnic/social group. (Can't claim to be French and not speak it.)

2. The harder it was to check out your new identity, the better. (The Nazi party archives were captured intact, with member photos. Hunted groups like the SS had unique blood type tattoos under their arms, and allied soldiers almost always checked prisoners for those.

3)You better have sympathetic locals willing to hide you or at least overlook any discrepancies.

Were there cases of Allied solders vanishing to avoid criminal charges at home or bad marriages for example?