United States Civil Administration of the Ryukyu Islands
In 1964, Warner retired from his faculty position to become the director of the Education Department of the United States Civil Administration of the Ryukyu Islands, on Okinawa Island. In the early 1970s he was the historian and curator of the US Armed Forces Museum on Okinawa, which closed in 1976. He continued practicing kendo, eventually reaching the 7th dan. He also reached the 6th dan in iaido. In 2001 the emperor of Japan awarded him the Order of the Sacred Treasure, 3rd class, Gold Rays with Neck Ribbon, for his accomplishments in the martial arts.