I didn't write this:
Any penetrating review of Okinawan weapons history is a mixture of hyperbole and fact.
Most modern martial arts students have been taught that Okinawan kobudo developed as a result of the Okinawan samurai being stripped of their weapons at two different points in their history. But a review of these incidents shows that our current view of the roots of Okinawan kobudo might be based on misconceptions.
The first time that the Okinawan samurai's weapons were supposedly confiscated was during the reign of King Shoshin (1477 - 1526). While it is documented that King Shoshin ordered his provincial lords, or aji, to live near his castle in Shuri, many historians no longer believe that he totally disarmed his ruling class. A famous stone monument, the Momo Urasoe Ran Kan No Mei, which is inscribed with the highlights of King Shoshin's reign, talks about the King seizing the aji's swords, and how he amassed a supply of weapons in a warehouse near Shuri castle. But some Okinawan historians now interpret that King Shoshin was actually building an armory to protect his ports and prepare for any potential invasion by wako, or pirates, not that he was stripping the Okinawan samurai or the general population of their weaponry.
The second time that the Okinawan samurai were purportedly disarmed was after the Satsuma invasion of 1609. But documents have been recovered that state that the Satsuma outlawed the ownership and sale of firearms, all the Okinawan samurai of the Pechin class and above were allowed to keep those muskets and pistols that were already in their family's possession.
There is further documentation that in 1613 the Satsuma issued permits for the Okinawan samurai to travel with their personal swords (tachi and wakizashi) to the smiths and polishers in Kagushima, Japan for maintenance and repair. From the issuance of these permits, it is logical to infer that there were restrictions on the Okinawan samurai carrying their weapons in public, but it is also clear evidence that these weapons were not confiscated by the Satsuma.
Based on this misconception that the Okinawan samurai were stripped of their weapons by the Satsuma most modern martial arts students are taught that Okinawan kobudo developed because the Okinawans turned to farm implements for their self-defense and training. When we consider the sai specifically we can see that the plausibility of this common myth is significantly strained.
Sensei Toshihiro Oshiro, long time practitioner of Yamanni-Chinen Ryu Bojutsu and the Chief Instructor for the Ryukyu Bujutsu Kenkyu Doyukai - USA, says that he has never found any evidence in his own extensive research to support the theory that the sai was used as a farming tool. Nor has he been told that by any of his teachers. He asserts that the sai has always been a weapon.
