Prewar Aikido seems to be the latest bugga boo here. So, to join in.
1) Prewar Aikido is Daito-ryu, the certificates say it, the sign said it, the students then said it, now all of you say it together, Prewar Aikido is Daito-ryu.
2) Daito-ryu has everything in it (that means what Takeda Sokaku taught). Five minutes into an Aiki Expo seminar by Kondo sensei of the mainline Daito-ryu, he had me down on the ground, sutemi fashion, in a grappling move with a pressure point application to the sternum and a neck crank -- all at the same time, certainly rivaling any Bjj'er. Saito Sensei handed out shuriken certificates out (Hendricks Sensei has one.) Jutte techniques are in the Gokajo section of the Hiden Mokuroku, sojutsu was taught to Ueshiba Sensei, variant Itto-ryu can be seen from the Takeda Tokimune sensei line and aiki can be seen from Kodokai and others.
3) Ueshiba sensei did two important things we should all be thankful. Simplified an ungodly complicated system which seems to have enough minutiae to fill a freight car and took out all the really, really, REALLY painful add-ons. How many people pin in suwariwaza by placing their knee on the triceps? Let me do it first. In ‘Budo Renshu' there is a drawing with the prewar pin variant with uke on his knees, bent at the waist and forehead touching the ground. This is to SLAM the skull to the ground, not gently guide uke into a life changing direction. Hell, I get enough injuries just doing Aikido, can you imagine what being hardcore back then must have meant. No wonder Takeda Sokaku's 10 day ‘classes' had a lot less participants at the end than at the beginning. "Uh, I have to go check up on my sick mother, sensei." There's a reason he had them pay first. There's a reason very few dojo practice yonkyo -- it hurts.
4) Ueshiba sensei was a tree-hugging, back to nature, new ager who dawdled excessively with some very, very fascist people. That's okay, everyone was fascist back then, just that U.S. was less than everybody else (thank God).
5) Did he change the direction of martial arts in Japan? I had a chance (unfortunately I didn't have a fortune to buy the rest of the books along with the last in the Soden series by Takuma Hisa -- the fish that got away) for a nice book translated as "History of Judo in Showa period -- with an appendix of waza - 1939" and the purpose is stated to help train the people's spirit for fascism (dirty word again). When you see Kano sensei in Europe who do you think he was demonstrating for in Germany, the local synagogue? Civilization came too close in 1941 to 1984 back then. O'sensei, though far on the fringes (what we would consider) with the utopian Omoto cult, took a superior deadly art, modified it like Kano had, looked at the precipice that wacky European thought had taken mankind to the edge of and said on the mat at least, "There is a better way." Did he believe it, I hope so. Did he bring spirituality into his new Aikido or did Daito-ryu have some of it in there anyway? Great question.
6) Ueshiba sensei had a student defect back to Daito-ryu (Takuma Hisa). Anyone can pick and choose to do the same, shades of one from column a and one from column b. He created a template (probably just like Takeda Sokaku) to study his way (whatever that is still being discussed), or go back to the roots of Daito-ryu, or follow the principles of physics and anatomy and diverge on a different path (I hear there is a combo of Yoshinkan Aikido and MMA -- aaaaaaaagh!) Of course, every seminar I have been too they always say their way is the right way, but it is a way to there.
7) Aikido's curves are rubenesque, with a projection not a crushing drop, a temporary pin and not a way to hold the body down while you cut the head off. It can have a lot less than the supposed nearly 3000 waza or it can have a creative riff with something new just showing up. It can be made too soft but that's alright when you get too old. It can be too spiritual but that can be better than too cauliflower ears. It's a way to there.
co-author of "Aiki Toolbox: Exploring the Magic of Aikido"