Re: Combat and war affecting the early training training of Aikido
I think that Peter and Kevin make good points, especially about the training that soldiers receive to prepare them for possible battle. This is a confounding variable in your thesis. You may be able to control for it by factoring in those soldiers who receive such training, but do not experience combat, and those who receive the same training, but do experience combat. Both cohorts, of course, are practicing aikidoka.
The military is made up of a large number of members that receive combat training, but are actually not part of the tip of the spear (unless things have changed significantly since I was in).
Of course, you will be relying on self-reporting here, but that is all you had to begin with anyway. Some soldiers, as Kevin mentioned, may be reluctant to share, but perhaps if they just limited their responses then to their pre/post aikido insights/thoughts, this may suffice for your needs.