Back to the war period.
I noticed that betwen the prewar and postwar pictures, O Sensei's appearance had dramatically changed. His hair had become completely white, he had grown a beard, he looked much slimmer and older. In brief, he became the O Sensei that we mostly remember him by today.
Do we have information on what could have explained this evolution, like health issues ? It seems to me that many people don't change that much between their late 50s and their mid 60s.
Morihei Ueshiba states in the sections I quoted in Column 7 and 9 that he was quite ill during the time of the second Omoto suppression, to the extent that he had major fears of an interrogation at the hands of the Kempeitai or Thought Police, who were not known for the delicacy of their methods, especially those interrogators lacking in 'kokoro'.
Ueshiba also states that he was quite ill at the time of the visions in 1940, even at death's door, but he then goes on to describe all the things he did for the Japanese government during this time. So it is hard to know how debilitating this illness was. There is an account of an earlier salt water drinking contest, which is supoosed to have a major effect on his health, but we do not know how serious it was.
Kisshomaru Ueshiba's biography is of little help here, since the picture he gives of O Sensei fluctuates between that of a frail person, of weak constitution, and that of a super-human, able to do great deeds right up till he passed way at the ripe old age of 86. Kisshomaru explains the illnesses of the later 30s and early 40s in terms of the burden of the war: O Sensei as avatar, suffering on behalf of the many. As a historian, I believe we need more evidence.
As for change in O Sensei's appearance, well, perhaps you should look at the present Doshu. I know that he has curbed the exuberant drinking habits of his youth, but in a very few years his hair has turned white and he sometimes looks quite haggard in appearance. The burdens of office? Possibly.