Karate was changed and used as propaganda. It's purpose was to instill national pride and foster the "samurai spirt" if you want to call it that. It was more a die for the cause brain washing institution. But non the less karate was high jacked for the war effort. However the sport mentality was mostly a case of survival after the war when America dictated all "national education PT" be stopped. This included martial arts. However on the grounds that karate and judo were deemed sports, it was allowed. Without this sport component martial arts would have been banned.
You will find no disagreement from me in any statement made here in. I will specify, that the following phrase:
America dictated all "national education PT" be stopped. This included martial arts"
Be modified to the following:
Allied Forces GHQ dictated almost all "national education PT" be stopped. This included all Japanese Budo martial arts, and an exception was allowed for Korean Martial Arts."
Sources:
When American
GHQ announced the
martial arts ban in 1945, students of Kanken Toyama's Shūdōkan opened a dojo studio called Kanbukan (韓武舘) to avoid the ban.
[2]
Attempting to create a more subtle name to disguise the organization, students used the name Kanbukan, which means "The Dojo of Martial Arts of Korea".
The director was a Korean called Geka Yung, while a top student of Toyama called Hiroshi Kinjo was the instructor.
He performed partner practice with direct blows using a
Bōgu (防具 protector) from
Kendo. This is Bōgutsuki karate.
[1][3]
In 1951 the ban was relaxed and Kanbukan was renamed Renbukan. In 1954 Renbukan hosted the world's first national karate convention.
In 1959, with the purpose to nationally organize Karate, the organization established the All Japan Karatedo Federation (JKF) and made Shūdōkan its overall headquarters.
[4]
The JKF appointed Choko Sai as chairman,
Yasuhiro Konishi (Shindo Jinen-ryu) and Hiroshi Kinjo (Kanbukan) as vice-chairmen, Kanken Toyama and Hiroyasu Tamae (Otou-ryu) as Shihan, and
Hironori Otsuka (
Wado-ryu),
Tatsuo Yamada(Nippon Kenpo Karate), Shinkin Gima (
Shotokan-ryu), Isamu Tamotsu (
Shorinji-ryu) and
Tsuyoshi Chitose(
Chito-ryu) as officers of JKF.
JKF Renbukai - Wikipedia
In short Koreans saved Japanese Karate!