What a question.

I don't even know how to meaningfully quantify the morale of a single man, let alone a troop of men or an entire service branch. Failing that I can't see a way to compare the morale of men in different service branches that will not be completely anecdotal. Morale tends to be one of those things glossed over by military historians in favour of things that can be quantified, debated, analyzed and structured. Logistics, training, equipment, strategy and so on tend to be the subject of intense study where morale might briefly appear as an afterthought. "Supply problems affected morale", "morale of the defenders finally broke" and so on. There tends to be relatively little academia on morale as such. If I were to attempt this, and do not that I am far from certain I can find academia supporting this, I would probably go about it like this:

What is morale?

Well. Paul Fussel defines it in Wartime: Understanding and Behavior in the Second World War as "Prevailing mood and spirit, conducive to willing and dependable performance, steady self-control, and courageous, determined conduct despite danger and privations, based upon a conviction of being in the right and on the way to success and upon faith in the cause or program and in the leadership, usually connoting, esp. when qualified by the adjective high, a confident, aggressive, resolute, often buoyant, spirit of wholehearted cooperation in a common effort, often attended particularly by zeal, self-sacrifice, or indomitableness"

I think that's a bit of a mouthful and would prefer, for the purposes of answering this specific question in this specifc context, to define it as "The mental capacity and willingness to preform a task".

Provided we are okay with my definition (or Fussel's I guess, we can move on to analyzing which factors affect that ability before we start looking at American Tankers and their counterparts in other countires.

What affects morale?

I would like to divide the factos that impact morale into three specific cathegories:

1. The very nature of war itself. (That which can not be controlled)
2. The factors with a secondary effect on morale (That which can be controlled but which does not exist specifically to promote morale)
3. Programs designed to target morale (That which can be controlled with morale as the primary target)

So let's talk, at least briefly, about these three factors and how they affect morale. To do this I will be talking a little about the Maslow hierarchy of needs because I think it makes sense to think of morale, at least on a fundamental level, in those terms since morale as I defined it above is closely linked to the Maslowian idea of motivation.

1. The very nature or war itself.
   War is, at it's very heart, about killing or dying. At least for the individual soldier. No one in his right mind would consider the risk of dying a factor that has a positive effect on morale, it's in the nature of war, you can't control it so you'll just have to accept it. War is also by nature a situation of scarcity, especially in the modern era. You are far removed from whatever comforts you are used to and for many, at least today, it may well be the first time they ever even have to think about their most basic needs.
   In Maslowian terms - Physiological needs. The nature of war itself is detrimental to morale/motivation. You are suddenly acutely aware of your most basic physiological need for homeostasis, safety, food, shelter, water and sleep. You can not control it, only do your best to mitigate the effects. The severity of these factors vary of course. I would imagine that even things like the environment would on a fundamental level affect morale. It stands to reason that the sense of familiarity with his surroundings for an American tanker in the European theater will make it less stressful than the experience of an American tanker in the Pacific. France is after all a lot more like home than the Pacific.
   Generally speaking it is the job of whatever the logistics and supply branch of the army to mitigate these factors as best it can.
   However, there is one factor that seems largely intrinsic to the nature of warfare that is not detrimental, the bond that seems to arise between soldiers who have shared experiences in war. This is described in a hundred different ways throughout history, all over the world. Let us call it Brothers in Arms for simplicity's sake. In Maslowian terms we are now moving somewhere up to Safety Needs and Social belonging. This brings us to point 2.
2. The secondary factors which have an effect on morale.
   If we look beyond the physiological needs of the soldiers but not quite up to deliberate efforts to improve morale I would like to paus at least briefly on two points I feel strongly affect morale even though it is not their primary functions. Leadership and training. Very, very, simply put these functions exist to ensure orders are conveyed and carried out and that the men who are supposed to do it have the physical capability and knowledge of how to do it. However, when done well, both also serve to strengthen morale through a variety of mechanisms. For example, familiarity breeds comfort. Having practiced something many times with a group of men who are going to do it with not only makes the task less daunting but also makes you more comfortable with the people you're doing it with. Both functions in effect strenghten morale. Leadership too has numerous ways in which it impacts morale, beyond firey speeches. Confidence in your senior officers promotes morale. These men have your life in their hands, trusting them not to throw it away is crucial. It is the same for junior officers and NCOs, these men not only lead you into battle, they are also usually (at least in the Western Tradition of Warfare) the men primarily responsible for unit morale. They, eat, sleep, shit, train and perhaps even die with you.
   However, these functions would still exist even if they had no effect on morale, they are required for a functional army.
3. Programs designed to target morale
   Here we find things like mail, movies, celebrity visits to the front, news coverage other related programs. There is no strict military reason for delivering mail to soldiers. We managed to fight wars for 1000's of years without any of the things above (but not necessarily without active morale boosting efforts). However, a letter from home, a parcel with sweets, cigarettes, gloves or other coveted items would certainly provide a welcome distraction from life on the front lines. The same goes for movies, shows, lectures and so on which might be made available in rear areas. These things serve no real purpose in war other than to improve morale and perhaps provide an alternative to the three traditional pastimes of soldiers in war, gambling, whoring and drinking as these might be detrimental to morale.
   In Maslowian terms we are talking about things that belong for the most part in promoting Social Belonging and Esteem. We're pretty high up in the Maslowian hierarchy now. A unit could probably function well without these things, at least for a time, if it had to.

Well that was a long-ass write up about, in part, my personal theories about morale and how it fits with the Maslowian hierarchy. So what about your question?

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