Yakage’s Yamajiro (Mountain Castles)
Long before Yakage became an Edo-period (1603–1867) post town, this area was an important stretch of the Old San’yō Road. The road connected ancient capitals such as Kyoto with western Japan, extending as far as the island of Kyushu. During the fifteenth and sixteenth centuries, as rival warlords fought to expand or defend their territory, keeping watch over major highways like the Old San’yō Road was crucial. Not only was the Yakage area a strategic location for surveillance, but it also had mountain terrain ideal for yamajiro.
Yamajiro were medieval fortifications built to utilize the mountainous terrain for defense, along with watchtowers and buildings to keep weapons and soldiers ready. Unlike later castles that were built with more permanent, elaborate structures for defense, yamajiro were simple wooden structures with extensive storehouses for supplies in case of a siege.
One of the most prominent yamajiro in the area was Sarugake Castle, built in 1205 by Shō Ienaga. His family was granted this area as a reward for meritorious service in battle, and his allied forces in faraway Musashi Province (present-day Tokyo and parts of the surrounding prefectures) wanted to keep this high-traffic area under observation. It was for this purpose that Sarugake Castle was constructed. It stood on a mountain next to the Oda River, and it had a close view of the Old San’yō Road on the opposite bank. Although steep terrain was a key defensive condition for many yamajiro, this mountain is so steep that even today there are sections traversable only by rope. Warriors in armor carrying heavy weapons would have found it a struggle to reach the castle, much less fight once they arrived. The Shō family successfully defended Sarugake Castle through fifteen generations until 1571. Four years later, Mōri Motokiyo (1551–1597), who was from one of the most powerful warrior families of western Japan, took possession of the castle.
Motokiyo needed a headquarters that was not only defensible under siege but prepared for other kinds of warfare as well. He moved the local Mōri forces to Mt. Chausu, a more easily traversable mountain with a clear view of the town, road, and river below. In 1584, the construction of Chausuyama Castle was complete, and in 1587, it became the base from which Toyotomi Hideyoshi (1537–1598) deployed Motokiyo to Kyushu to subjugate rival forces there.
The Mōri family, despite their control over much of western Honshu, ended up on the losing side of the decisive Battle of Sekigahara in 1600, and the Yakage area was among the territory they lost. In the relatively peaceful Edo period that followed, the shogunate limited the number of castles allowed to stand, and Yakage’s castles and other yamajiro across the country were abandoned or torn down. Today, at the site where Sarugake Castle once stood, the mountain still presents a challenging climb, and remnants of the castle’s stone foundation can be observed along the way. The site of Chausuyama Castle is a quiet park with a view overlooking the town of Yakage.
