Toyokawa Naval Arsenal Ruins

The Toyokawa Naval Arsenal (豊川海軍工廠) was one of the Imperial Japanese Navy's most important ordnance production facilities during World War II. Plans for the arsenal were drawn up in March 1937 alongside the Suzuka Naval Arsenal, and construction began on October 1, 1938, on a site in what is now Toyokawa City, Aichi Prefecture. The facility commenced operations in 1939.

By 1940 the arsenal had expanded to approximately 330 hectares (815 acres). The northern 60 percent of the grounds was devoted to gunpowder and ammunition production, while the southern 40 percent housed machining and assembly workshops. The factory's primary output included the Type 92 7.7 mm aircraft machine gun, the Type 99 20 mm aircraft cannon, and various naval ordnance components. At its peak, the arsenal employed over 56,000 workers, including thousands of mobilized students — schoolchildren and teenagers conscripted or volunteered into factory labor under Japan's wartime National Mobilization Law.

On the morning of August 7, 1945 — one day after the atomic bombing of Hiroshima — 131 B-29 Superfortress bombers of the USAAF 20th Air Force launched from bases on Guam, Saipan, and Tinian, of which 124 bombed the arsenal; 52 P-51 Mustang fighters stood by over Izu Ōshima in case the bombers were diverted to their secondary target and did not accompany them to Toyokawa. The formation arrived over Toyokawa at about 10:13 AM and bombed for 26 minutes. The arsenal was the target, but bombs also fell on the surrounding area and civilians were among the dead. A total of 3,256 500-lb general-purpose bombs (approximately 813 tons) were dropped from altitudes of 15,000–17,000 feet.

The devastation was catastrophic. Casualty estimates range from 2,544 to about 2,800 killed (the city history gives 2,667), with thousands more wounded. Among the dead were 452 students (193 boys and 259 girls) who had been mobilized to work at the arsenal. Japanese anti-aircraft fire damaged 21 B-29s during the raid; one crashed into the ocean near Iwo Jima. The arsenal was effectively destroyed, and much of Toyokawa's urban center was reduced to rubble.

After the war, the former arsenal grounds were converted to civilian use. Parts of the site became residential areas (Honohara 1st and 2nd districts, Suwa 1st district) and industrial zones. In 2018, Toyokawa City opened the Toyokawa Naval Arsenal Peace Park (豊川海軍工廠平和公園) on a preserved section of the former grounds. The park features the Toyokawa Peace Exchange Hall (豊川市平和交流館), which exhibits wartime artifacts, survivor testimonies, and scale models of the arsenal. Several original structures survive within the park, including reinforced-concrete ammunition storage bunkers and foundation piles, serving as tangible reminders of the tragedy. Annual memorial ceremonies are held on August 7.