At times modern martial discussion derides the changes to Karate sponsored by Itosu Anko as school boy karate. I believe the truth is quite different. He created a simplified and standardized training which was used in the schools and later many karate programs.
Okinawa was a loyal part of the Japanese Empire. When Itosu Anko drafted his famous 10 precepts in 1908, He was trying to show officials of the Ministry of Education, positive values offered by training youth for eventual military service.
While there were Okinawan’s who avoided the draft and visited China, most Okinawan’ s didn’t do so. I imagine the goal was to teach youth to be used to follow orders and become stronger physically. Military training at that time was far beyond hand to hand combat.
Where Itosu wrote:
“The purpose of karate is to make the muscles and bones hard as rock and to use the hands and legs as spears. If children were to begin training in Tang Te while in elementary school, then they will be well suited for military service. Remember the words attributed to the Duke of Wellington after he defeated Napoleon: "The Battle of Waterloo was won on the playing fields of Eton."”
“When you train, do so as if on the battlefield. Your eyes should glare, shoulders drop, and body harden. You should always train with intensity and spirit, and in this way you will naturally be ready.”
“..then we will produce many men each capable of defeating ten assailants.”
It certainly helped make his case.
There were many instructors who taught school students.
Then Funakoshi made the case when he took karate instruction to Japan. There he worked with the Universities and the Naval War College making the same points.
Of course the Japanese military at that time was occupying Korea and Manchuria.