***the military cigarette ration was to tide you over if additional food was delayed.***
People inhaled cigarette smoke different back in those days. You sucked the smoke into your mouth, then swallowed it to your stomach, then burped it back up and blew it out. All this bypassed the lungs.
Later they sucked it into the lungs.
Nasty either way.
I also think that is was just a distraction with a nicotine rush replacing the energy provided by food.