Just a thought, but if you want to know the effect of war/combat on someone's aikido training, I am sure that there are a lot of current combat veterans out there who have practiced aikido before going off to war and who resumed their practice after they returned. Their experiences and thoughts might prove useful, and while they are not Morihei Ueshiba, their insights might provide you with some perspective.
Been away for a bit. Were there any specific correlations you wanted to discuss? Its a bit of a broad topic and difficult for me to narrow down.
I think positive effect from my aikido training ranges from simple environmental conditions to situations involving imminent dangers. Much of my training has been focused on the development of the self, wherein one can be positive, happy even, without attaching those emotions to any specific person, place, or thing. My teacher calls this 'bliss,' or happiness for no reason. This may sound esoteric or even a little cooky to some, but to me its an invaluable life skill. While not possible all of the time, even making the attempt, in my experience, can make a positive difference. This idea would be the epitome of training in the budo, but other aspects have/had effect as well. In a macro concept, this 'bliss' training effects all one does...whether its simply thriving in pervasive arduous conditions, being away from home, etc or managing immediate feelings such as stress, fear, and rage.
Specifically, concepts that I've spent some time thinking about (at the behest of my teacher) are Japanese philosophies, ishi, such as malobashi (just do it), or shinken shobu (sword battle to the death). Please excuse any poor translations on my part. While there are many other ideas I've studied in my aikido training, these are two that popped into my mind. Malobashi is an idea of not hesitating, jumping in with both feet. This takes some level of courage, coercion, or pressure but is important in developing one's self. I had moments of reticence when getting ready to 'step off' on a foot patrol on many nights, well every night, due to the quantitative presence of improvised explosives in the area. While one may argue that I had little choice in the matter, there still has to be a cognitive decision made that you are okay with this. That you are going to accept this and be at peace with it. Not push fear aside, or amuse yourself with distracting thoughts...but to actually embrace and 'be ok' with what you are about to do...regardless of the risk. Acceptance and action...malobashi.
These concepts blend together making it hard to tell where one begins and another ends...the delineation, in particular when applying to personal situations, becomes a bit foggy. Anyway, the idea of shinken shobu, is to treat life, a particular situation, with the seriousness of a battle to the death. Obviously one needs to be focused when facing such a situation as facing off with an opposing, talented, swordsman. Not much in contemporary life has such an immediate impact. But acting like it does, when appropriate, can bring clarity, seriousness, and focus to a task or situation at hand. Technology and society often allow us to be in 'cruise control' much of our day. This idea is to take us out of that quasi-meditative state and bring lucidity to what we are doing at the moment. Nothing quite brings this home like an actual life or death situation. And again, going back to malobashi, it is important to accept the situation for what it is and act accordingly. Specifically, right after having a sniper round whiz nearby my head (I was being stupid, cocky, and standing up in a place I should not have), I dropped quickly down into my little fortified rooftop post. Immediately follow-on gunfire from RPKs and AKs impacted accurately on the compound and sandbags on the roof. Laying down as low as possible, my friend and I were trying to figure out how to get up and get to the machine gun in the opening of our position. Stuck in indecision, eventually we realized we needed to do something as doing nothing was not getting us anywhere. The above-mentioned concepts actually came to me at that moment, and I decided action was necessary, even though any attempt to return fire would expose us to great risk. My friend grabbed a small periscope near us and poked his head up as quick as he could to identify the point of origin of our attackers while I popped up on a gun and fired in the direction he called until incoming firing slowed down and I could take a moment to properly obtain sight picture and return fire a little more precisely.
While I understand these are all things regularly done by many people who do not train in aikido, I feel my training had positive effect in my ability to cope with these types of situations both at the time, and the follow-on repercussions.
To me, physical training in aikido is an integral part of this. The human body is limited to its physical mass and, it is my opinion, the physical mass must be broken down before true development of the spirit is reached. Sitting and meditating is a great discipline, but I feel the physical side of personal growth is key in reaching sanguine meditative states while executing extreme physical feats. For example, doing 1,000 breakfalls, knee walking until the skin is torn from the knees; knowing, receiving, and accepting pain...all these things breach physical barriers, break down the physical elements, and expose the ability to develop non-physical aspects of oneself by allowing the spirit to be forged. Even displaying archaic etiquette, respect, and seriousness to training has helped in my development. These techniques we do can be seen as metaphors for obstacles in life, or obstacles to self-growth. Pushing oneself beyond what they thought possible, literally when someone says they can physical do no more...make them do three more...and hopefully, if their mind is right, they will not quit and will allow their body to improve their spirit. Once on barrier is breached, hopefully the idea that there are no barriers will seep in to one's subconscious and conscious mind. I understand this is a really 'glass is half full' approach to life, and training, but I find that even making the attempt of conceptualizing this can result in improvement to one's life.
But that is me, and my reasons for training. In my life, this approach to training has proven much more practical than focusing on aikido as a format for self-defense or physical fitness. Its helped me professionally and personally, making aikido a 'focus' in my life from which benefits all other pursuits.