Flag of the Ryukyu Islands

A modified delta flag was once used in Okinawa Prefecture of Japan when it was placed under United States military occupation from 1945 to 1972, under the name of the Ryukyu Islands. While Japan as a whole was under the Allied Occupation, the Supreme Commander for the Allied Powers (SCAP) showed its intention to separate Okinawa Prefecture and the southern part of Kagoshima Prefecture from Japan in 1946. The Treaty of San Francisco of 1951 indicated that Japan retained "residual sovereignty" over Okinawa, the U.S. military banned the Japanese national flag for a long time.

U.S.-occupied Ryukyu Islands for vessels

Name	signal flag delta
Proportion	Various
Adopted	1952
Relinquished	1967

In the immediate aftermath of the war, Okinawan merchant ships adopted the D pennant as a naval ensign. However, because the pennant was not recognized as a naval ensign and was not well known, many ships flying the pennant were seized.[1] Eventually USCAR made the Flag of the United States the naval ensign for ships from the Ryukyu Islands,[2] but many Okinawans opted for the Hinomaru in protest. In 1967, a new naval ensign was approved for use by Okinawans by USCAR; it was the flag of Japan with a pennant that read "Ryukyus" and "琉球" (Chinese characters for "Ryukyu") above it.[3]