Takeda was known to switch hands when holding a bokken. Ueshiba did, too.
Mark, I've never heard this before about O Sensei. Where have you read or seen this?
I mean let's face it, he came from an informal Itto ryu and Jikishinkage ryu background into watching/ possibly training (I'd bet on it) informally in TSKSR and KSR and Yagyu.
Dan or anybody, what was the Katori connection? I am aware that O Sensei had a high-level Yagyu Shinkage ryu swordsman train with him, and he sent Kisshomaru to train in Kashima Shinto ryu. I am not sure if I've read anything tangible about a connection to Tenshin Shoden Katori Shinto ryu.
My two cents, Ueshiba lived a life where there was a good deal of "ambient" sword training going on, but it doesn't seem to me that he ever pursued sword training for its own sake; I don't think he went through a traditional shu ha ri process inside a koryu.
Takeda no doubt showed him plenty of swordwork, and other weapons - but it doesn't seem to me that he formally trained him in Ono ha Itto ryu, or else you'd see a lot more of that school in modern aikiken. So its best to say, the stuff he learned from Takeda was "informed" by Ono ha Itto ryu and Jikishinkage ryu.
Ellis's Hidden in Plain Sight
mentions that Ueshiba had a student who was a high-ranking Yagyu Shinkage ryu swordsman, and there is the case of the YSR menkyo given to Ueshiba by Takeda that still boggles my mind - I accept that it happened but I still don't understand what it actually was.
We know that Kisshomaru was sent to train Kashima Shinto ryu, and that O Sensei was also entered into the roles there. In my very humble opinion, there is no stronger influence on Saito Sensei's aikiken than Kashima Shinto ryu. I understand that Saito Sensei did NOT train Kashima Shinto ryu, so this to me indicates that Kashima Shinto ryu was actually the most significant koryu kenjutsu influence on Ueshiba. (Unless Saito's aikiken actually comes from Kisshomaru...)
But hey - he also trained Yagyu Shingan ryu for some time, right? That school has sword. And I believe its a Kashima-descended system as well - straight bokken and all that.
Who knows what else he may have picked up while serving in the army. He practiced jukendo - did that have any sword component? And what's the deal with the time, place, and class that he grew up in - did kids go at each other with bokken? Might be a silly point, but I think the deal is that swordwork was always around, adjacent to what he was working on. I think he thought it was perhaps boring, perhaps archaic, perhaps shallow. But I am pretty sure he was trying to make Aikido something that superseded the sword, went beyond it.