Greater Naha-Shuri defense network

The Greater Naha-Shuri defense network (Japanese: 大那覇首里城道 Dai Naha Shuri jō dō, Okinawan: 大那覇首里城道 Ufu Naafa Shui gushiku duu) is a series of fortifications, roads, and warehouses in and around the Naha-Shuri metropolitan area.

History
The entire defense network was built by King Shō Shin at the turn of the 16th century, although it was also improved upon by later Kings. It is centered around the defense of Shuri Castle and Naha Port. It consists of five castles, the Pearl Road, and numerous warehouses. The system was extremely effective against naval attacks directly against Naha, however its weaknesses were shown during the 1609 invasion by Satsuma Domain, speciffically that it left Shuri Castle vulnerable to an overland attack. It would continue to defend Naha from pirate attacks until the mid 19th century. It was partially utilized by the Japanese military before and during World War 2. Most of the defense network was destroyed in the Battle of Okinawa or during the expansion of Naha Port by the American military.

Castles

 * Shuri Castle (首里城) - royal palace
 * Tomigusuku Castle (豊見城城) - command center
 * Iō Castle (硫黄城) - primary armory and arsenal
 * Mie Castle (三重城) - northern harbor entrance defense
 * Yarazamori Castle (屋良座森城) - southern harbor entrance defense

Roads

 * Pearl Road (真珠道) - ring-road between Shuri and Naha connecting all major components