Actually there was - one. Germany in WWII.
The POWS in Luftwaffe and Wehrmacht camps were treated in accordance with the GC.
In fact the Soviet soldiers in the German POW camps did not want to be repatriated back to the USSR, but they were. Then Stalin killed them and/or sent them to Siberian Gulags for 'treason'.
Agreed, but it was not the entire country, only some camps as you state. German high command eventually ordered that all pilots captured be shot.