I'm serious about this, and I'm playing with some inquiry. Since the Bronze Age, the sword had been the height of martial technology. In the pre-war era Morihei Ueshiba appears very warlike and grimacing. Like he was going to tear you a new one. Contrast that to post-war aikido, after the atomic bomb, and there is a smiling older man running around with his arms raised towards the sky and declaring peace.
M. Ueshiba had several "conversion" experiences over the years, beginning in the 1920's. But it wasn't until WWI and his direct experience of another type of destructive power, the atomic bomb, that things appear to completely transform, and he makes a complete 180.
I think there have already been some great posts here; I have little to add in the way of supporting my own opinion, that the war and the public face of aikido were correlated, but probably not directly related. Nor do I believe that O Sensei modified his vision of budo from the older concepts. Likely, the softening of those edges where Doshu.
I think you could find a similar (and perhaps stronger) argument to support a claim that aikido is based upon the concept that came from the end of WWI and rebirthed following WWII - the conceptualization of a league of nations, inter-related economically and culturally in a such a manner as the overt declaration of war upon one nation would necessarily damage the league as a whole, thus deterring one member from considering such a harsh decision as to declare war upon another country. Of course, this is anecdotally constructed and loosely based upon previously successful social[ist] propaganda of that time.