A few years ago I happened to catch a program dealing with military training and the reactions of soldiers. It was the premise of this show that the vast majority of the fighting that was done in WW II (and most wars up to this point)was done by relatively few men. I believe they quoted around 15%. The others just clutched their rifles and tried to stay hidden. Several WW II veterans disagreed with this figure, but apparently there was substantial evidence supporting it.
As a result of this, the marine corps (and probably the army as well) significantly changed their training regimen. The new training worked on the 'Pavlov's Dog' principle. Soldiers were drilled over and over again to perform certain maneuvers until they would do them automatically under combat conditions. The idea being to brainwash these men into becoming killing robots.
With the new training, the number of soldiers who actively participated in battle rose significantly. I believe it was around 80% in Vietnam. However, the training regimen also had the unfortunate side effect of making it extremely difficult for these men to readjust to normal society (it seems there's limited job opportunities for brainwashed killing robots in the corporate world).
Nothing real earth shattering, I realize. I was wondering, however, if your research agreed with these figures.