Site of Kaneda Fort
Tsushima Island’s Kaneda Fort was a sprawling mountaintop stronghold built by the Yamato government in the late seventh century as part of a network of fortifications established to protect Japan from an expected invasion by Tang China and the kingdom of Silla on the Korean Peninsula. Long sections of the fort’s stone walls, which are up to 6 meters high, remain on the slopes of the 276-meter Mt. Jo at the southern end of Aso Bay in central Tsushima. The Korean Peninsula is visible from the summit on clear days.
The Yamato court feared an imminent attack from mainland Asia after the year 663, when the Tang–Silla alliance subjugated the Korean kingdom of Baekje, a longtime Yamato ally, leaving Japan alone in East Asia to stand against the might of the Tang. Baekje officers and engineers who had fled across the Sea of Japan were recruited to construct Korean-style forts on the border islands, in Kyushu, and along the shores of the Seto Inland Sea—the likely route the enemy would take toward the capital of Asuka in present-day Nara Prefecture.
Kaneda Fort was the first line of defense in this network. The sheer cliffs of Mt. Jo made securing the fort’s western side easy, while high stone walls were built on the eastern side and up around the peak to repel intruders. Entrance to the fort was from the south through several gates that led to a flattened section on the eastern hillside. The guards stationed at the fort are thought to have lived in this section and patrolled the walls and summit in shifts.
The Tang–Silla alliance fell apart before any invasion of Japan could be carried out, and Kaneda Fort lost its significance. The site was converted into a modern military facility in 1901, when Imperial Japanese Army engineers built a road to the summit and installed a cannon battery on it. The 2.4-kilometer hiking trail to the peak uses this road, passing several sections of the ancient stone walls along the way. The climb takes around an hour in favorable weather.