A super interesting video interview with Tamura Shihan who was O Sensei's favorite sword ukes.  Tamura Sensei was a huge propagator of Aikido in Europe and especially France.  Perhaps O Sensei liked his sword ukemi because Tamura Shihan's father was a Kendo teacher.  Tamura Shihan passed away in 2010 at the age of 77.  I found this interview incredible enlightening.  Anyone interested in studying Aikido should watch this video, but it also might be incredibly helpful to students who already practice Aikido.  He succinctly sums up not only training but motivation as well. https://www.youtube.com/watch?v=SPeSKlkKPOg