Former Matsuyama Naval Air Base

The Matsuyama Naval Air Base was established in October 1943 in the Minami-Yoshida district of Matsuyama, Ehime Prefecture, on the coast of the Seto Inland Sea in Shikoku. The base was constructed as part of the Imperial Japanese Navy's effort to establish fighter defense networks across the home islands as the war situation deteriorated.

The base achieved its greatest fame as the home of the 343rd Naval Air Group (Dai-343 Kokutai), nicknamed the "Tsurugi" (Sword) Unit. Formed on December 25, 1944, at Yokosuka, the 343rd was the brainchild of Captain Minoru Genda, a brilliant tactical planner who had helped devise the Pearl Harbor attack. Genda believed Japan's declining fortunes could be reversed by concentrating the best surviving pilots and equipping them with the most capable fighter aircraft available.

The unit was equipped with the Kawanishi N1K2-J Shiden Kai ("Violet Lightning Modified"), Allied code name "George," widely regarded as the finest fighter produced by Japan during the war. The Shiden Kai could meet the F6F Hellcat, P-51 Mustang, and F4U Corsair on equal terms. The 343rd comprised three fighter squadrons -- the 301st, 407th, and 701st -- each staffed with veteran pilots, many of them surviving aces from earlier campaigns.

Genda assumed command on January 15, 1945, and by late January the unit had concentrated at Matsuyama, chosen for its central location relative to potential defensive zones over Shikoku and western Honshu. The unit's baptism of fire came on March 19, 1945, when approximately 350 US carrier aircraft attacked Kure Naval Base. Fifty-four Shiden Kai fighters scrambled from Matsuyama and engaged the American formations in what became known as the Battle of the Skies over Matsuyama, one of the most intense air battles over the Japanese home islands.

To protect its aircraft from Allied air raids, 63 aircraft revetments (entaigo) were constructed around the base in the Minami-Yoshida and Kakio districts. These reinforced concrete shelters featured distinctive barrel-vault arch designs. The 343rd continued operations against US carrier aircraft and B-29 bombers until the end of the war; from April 1945 it operated mainly from bases in Kyushu, and it was at Ōmura when Japan surrendered.

Today, the former airfield serves as Matsuyama Airport. Three of the original concrete revetments survive in the Minami-Yoshida district south of the airport. One shelter, measuring 23.1 meters wide, 12.25 meters deep, and 5.12 meters tall, was designated a Matsuyama City Tangible Cultural Property on May 18, 2018, and has been open to the public since November 28, 2020. They are among the notable World War II aviation relics remaining on Shikoku.