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Remains of 7th century smoke signal site found near ancient Japanese capital

This Dec. 10, 2020 photo shows the remains of a smoke signal platform in Takatori, Nara Prefecture. (Mainichi/Honsu Kan)

TAKATORI, Nara -- Remnants of a smoke signal site dating back to late seventh century have been found at the Sada Takayama ruins in this western Japan town, the local education board announced on Jan. 20.

    The "Nihon Shoki" or "Chronicles of Japan," completed in 720 and believed to be the second oldest book on Japanese history, relates that a smoke signal system was established between the southwestern island of Kyushu and Asuka in present-day Nara Prefecture, where the Imperial Palace was situated. The system was meant to transmit warnings of foreign invasion, after Japan suffered a crushing defeat in the Battle of Hakusukinoe in 663 against the allied forces of China's Tang Dynasty and Korea's Silla Kingdom. The recently discovered site is thought to be a part of that system.

    The site is the first definite one of its kind discovered, and one expert said "the find gives us a nearly complete picture of ancient smoke signals, which had been uncertain."

    The ruins of a smoke signal platform, a large-walled building and a structure using pillars embedded in the earth, were found in a line on the top of a 30-meter-tall hill during a test excavation to replace a Kansai Electric Power Co. transmission tower. The platform is a mound with a vertical, chimney-like hole about 2.7 meters deep. Dry grass and other materials were apparently lit and fanned in the bottom of the structure to produce smoke, and traces of use, such as black soot on the wall, were found.

    The large-walled building has pillars sealed with soil, a technique unique to people who came to Japan from continental Asia between around the fourth and seventh centuries. Some of these people who had settled locally may have been involved in constructing the building.

    The Nihon Shoki says that soldiers and smoke signal sites were deployed in 664 on the islands of Tsushima and Iki north of Kyushu, as well as Tsukushi province in present-day Fukuoka Prefecture, and moats were constructed to protect Dazaifu -- a regional government center in northwest Kyushu. The book also states that the military code of the day laid out how the signals should be used: smoke for the daytime and fire at night, with sites spaced some 20 kilometers apart and an officer assigned to each.

    According to the Takatori education board, the large-walled building is thought to be for the detachment manning the signaling station. The embedded pillar structure is likely the office of the public bureaucrat who oversaw the platform.

    "We could say these findings indicate that people actually tried to relay signals to Asuka, not just that the system was built," said Takafumi Yamada, a researcher at the Archaeological Institute of Kashihara, Nara Prefecture.

    The remains of a similar structure were found in 2002 at the Morikashidani ruins, about 600 meters south of the Sada Takayama ruins.

    Nara University associate professor of Japanese archaeology Yoshiyuki Aihara commented on the latest discovery, "It means that a part of the defense network to protect Asuka has been found," adding, "These findings at the new site and the Morikashidani ruins have gradually revealed what the ancient smoke signal platforms were like."

    (Japanese original by Honsu Kan, Nara Bureau)

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