This topic had been discussed before in the Aikido Journal forum.
This is from one of the posters:
I actually read the letter yesterday when an original was found in our dojo archives. It was about 4 pages and was extremely heartfelt. In fact it was dated in April but it was a letter of resignation as Shihan bucho of the aikikai effetive April 30th 1974. It spoke a lot of the history and how it came to a point that he felt ki was being completely neglected in teaching at tokyo HQ. It also spoke of how powerful the Yoshinkan group had become and how he collected money from the USA during his first visit in 1953 to rebuild Aikikai HQ. He told how it was the Nishi kai that invited him to Hawaii to spread aikido and not O'Sensei. Although he did obtain Ueshiba Sensei's approval I am sure.
It spoke about how Yamada Senesi created the USAF and to his dismay became president of the organization. Tohei Senesi felt that an american should be president of the organization. I know Yamada Sensei and Tohei Sensei have since buried the hatchet when yamada sensei went to meet with Tohei Senesi in the 80"s or 90's and donated money to Ki No Kenkyu Kai HQ.
Above all it was an extremely respectful and heartfelt letter.
Link to the post http://www.aikidojournal.com/forums/...9c243354f0884d
It's been a long time since I read that letter (and I don't have a copy anymore), but as I recall I didn't find the tone nearly as respectful as the poster in the e-Budo thread seemed to.
What I'd really like to see is the response to that letter that was written by Tadashi Abe.
On a side note, there was always some rivalry between the Yoshinkan and the Aikikai as the developed in parallel after the war (Shioda and Kisshomaru were sort of like older and younger brothers in many ways), but I'd note that they managed (and still manage) to maintain close and cordial relations through the years.