Aikido is based on sword movements
It's not just Aikido, it's almost all the Japanese Ju-Jutsu that is based on sword work. Japanese Ju-Jutsu started evolving in a period of internal warfare. Weapons were the main subjects of teaching,rather then empty hand. Even the sword was not the first weapon of choice.
As the internal war subsided, people started having more need for un-armed combat, and they developed it from the basis they had - weapons work. The great emphasis on sword work comes from the place the sword had taken in Japanese culture.
Looking at the technical content Ueshiba Aikido is very similar to Daito-Ryu Ju-Jutsu (As experts who learned both M.A. state, I have not practiced either for long period of time). As such it uses the same basis - sword work.
have alot of difficulty with people saying "Aikido principles are based on the principles of the sword". One cannot argue that Ueshiba M. trained with the sword and it influenced his understanding and creation of Aikido, however I would argue that both the sword and Aikido are based upon the same principles...not that one came before the other...just that they both use similar understanding of body dynamics and movements.
I have to both agree and disagree: learning Korindo Aikido which combines a lot of weapons work and empty hand, the saying goes "When empty handed think of using a weapon, when holding a weapon, think of being empty handed". Almost all the principles of empty hand and weapons work are the same, many techniques borrow from one side to the other, and I have improved more then one empty hand technique after learning a similar move with some weapon and visualizing it when practicing empty hand.
On the other hand, weapons often use different mae (distance). In some ways, learning each weapon gives more emphasis for different principles. A short and very incomplete list of ideas that are more emphasized with some weapons would be:
Boken - one body, taking the center, very exact feeling of mae.
Wakizashi (against Ken)- closing distance, avoiding the center.
Jo - Taking the center, flexibility in changing sides.
Ni-to (2 swords) - Using the body for two semi separate movements.
(It is possible to extend this list, but those are the first things that came to my mind today)