While we are on the subject of ranking, there is an interesting story about the history of Isshin-ryu karate-do. I don't know where it falls on the spectrum from absolute truth to apocrypha to pure B.S. but I've heard this piece of 'history' from several sources over the years.
The story goes that Shimabuku trained a bunch of American GIs during wartime and having earned shodan or nidan they left Okinawa and brought Isshin-ryu to the United States (that much is mostly fact I think). Some years later, it seems, his students organized a trip to see and train with Shimabuku, and the Master, knowing that these were all dedicated students that he might never see again, issued them certificates for each rank up to Roku-dan (6th degree black belt) with the understanding that they were not to claim those ranks until they had proper time-in-grade and practice.
Effectively, Shimabuku promoted his inner circle - the folks that would become the Isshin-ryu demi-gods from shodan to rokudan.
Again, I don't know how much of this tale is true, and I don't intend this to scandalize the Isshin-ryu folks. Shoot, the most skilled karateka I've ever met and laid hands on are Isshin-ryu folks. I just thought the story was interesting while we were talking about ranks and jump promotions.
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