In the days of the Ryukyu Kingdom, from the 14th to 19th centuries, Chinese envoys would come to Shuri Castle on the island of Okinawa to officiate at the coronation of the Ryukyu kings. When their ships were spotted from the 227-meter peak of Mount Akama on the northeast coast of outlying Tokashiki Island, smoke signals announcing their imminent arrival would convey the news back to the main island.
But in 1879, the Ryukyu Kingdom was annexed by Japan — then recently free of the Tokugawa Shogunate's feudal yoke, and with the Emperor Meiji installed as its symbolic head — and such visits from China came to an abrupt end.
For several decades afterward, Okinawan life continued largely unchanged in its peaceful, bucolic way. But all that came to an end when the enemy in World War II began to get ever closer following the Imperial Navy's catastrophic losses in the Battle of Midway in 1942.