To answer the question, we do not really know if most were addicted. Simply because we do not have the data, normally such data would be collected at enlistment and in cold war the military started to collect such data, which gave enormous amounts of data for research. Yet in the WW2 such data was not yet collected and probably would not have been as other "things" like the war were more important.

But returing to your question. What we can say is that the numbers might have increased as people that were restricted through religious or simple familly morals were barred from smoking came in enviroment where it was tollerated. Furthermore, like you al ready mentioned a cigarette was a last consolation, but in the situtation that such would be needed it was to dangerous to smoke. In heavy artillery fire, you would be screaming or "biting dirt" for cover, laking the attention of abillity to smoke. Similiar in combat as liting up a cigarette might give away position or take away attention and fighting ability from combat.

Were the real use of cigarettes lay for the soldier and military was before and after combat and in the long waiting periods between combat situtation. In the first case, nicotine calms the people down and in war you are confronted with extreme amounts of stress. The stress and fear of expactetion of combat and of course that of combat itself and after it, you are faced with the of lowering adrinaline and regaining awarness of your stress, fear and fatigue. in those case a cigarette is perfect to calm the soldier down, while easing the pain and fatigue. So mentaining combat ability. of course, it would not make you fit again and the effect differ from person to person, yet it helps. In the later case, what people often forget or do not know about war is that it is not action after action, there are a lot of long periods were nothing happens. War is often long dull periods of waiting. In that situations soldiers need something to do, drill and maintance are more common is the answer, yet those task are themselves dull and standing guard is even worse. Smoking helps to pass time and keep the mind calm. In periods of boredom people think, and in war this not always desirable as it cause a down fall of moral (Home sickness, longing for loved ones, questioning the usefulness of war). Another element is that rolling cigarettes is something to do in times were there is nothing to do. One reason for the popularity of pipes under soldiers during war, it takes longer to smoke and maintance takes more work and time, perfect for such situations.That are the points of usefullness of smoking and why one would start and why it is support.

From this we can look on the concrete answers to your question. I have showed why the army supported giving out cigarettes in ration packs. The second reason and most important one is, we are speaking about the 30's and 40's smoking was common and well most people accepted it as somthing natural, (in the first half of the 20th smoking became for everyone social exceptable, even women). So large amount of the people would have smoked and been addicted. Smoking addiction was not seen as an addiction a such, just as a habbit. No one knew about the neagtive effect of smoking, it was even given to ashtma patients to help with thier breathing. Yet the withdrawal effects were known. Would you want hunderd of thousands of soldiers going through withdrawal symptoms while fighting the enemy? It is a garantee for disaster. So, most soldiers would have already been smoking and the amount that would have taken up something would be not more than normal for the time. And yes, a lot might have been addicted when returning, yet again not more than normal. Though, not everyone that smoked during the war was addicted and a significant number would have droped it after the war, as it was war time habbit.

Finally, we should not forget a lot of soldiers did not smoke, they just did not want to or did not like it. For those soldiers these cigarettes were also quite important. The could trade it with other soldiers for thing that they did want or even with friendly civillian population (shortages, even with the best logistics of the world are always common). Cigarettes are a major currency in time of war or crisis were the normal money has lost it value or is not excepted.