WW2 field rations were revolutionary for the time, and US troops rarely went unsupplied (Axis forces often had missing food supplies all the time. The Japanese and Russians had it particularly bad). But the field rations were often described as being unfilling and didn't provide enough calories as needed. But they were not as bad as many people make them out to be. Granted if I had to eat nothing but those rations for weeks on end I'd be a very sad soldier.