Mitsubishi Nagoya Engine Works (Daiko Plant)

The Mitsubishi Heavy Industries Nagoya Engine Works (三菱重工業名古屋発動機製作所), commonly known as the Daiko Plant (大幸工場), was Imperial Japan's most important aero-engine manufacturing facility during World War II. Located in Daiko-cho, Higashi Ward, Nagoya City, Aichi Prefecture, it was the powerhouse behind Japan's wartime aviation, producing more aircraft engines than any other single factory in the country.

Establishment and Organization

The Daiko Plant was formally established on July 1, 1938, when the engine manufacturing division was separated from the Mitsubishi Nagoya Aircraft Works at Oe (大江工場), which continued to focus on airframe production. This organizational split reflected the enormous scale of Japan's wartime aviation industry — the Oe Plant designed and assembled complete aircraft (most famously the A6M Zero fighter under chief designer Jiro Horikoshi), while the Daiko Plant concentrated exclusively on engine production. Together, these two facilities formed the twin pillars of Mitsubishi's Nagoya aviation complex, though they were located several kilometers apart.

Engine Production

The Daiko Plant produced a remarkable total of 48,996 aero engines by war's end according to commonly cited figures (Mitsubishi Heavy Industries' own company history gives about 52,000), making it, with Nakajima, one of Japan's two great engine manufacturers. The primary engine types produced here included:

• Mitsubishi Kinsei (金星, Venus): A 14-cylinder twin-row radial producing 1,060-1,560 hp depending on variant. Over 15,124 Kinsei engines were produced across all variants. It powered the Aichi D3A "Val" dive bomber (the aircraft that struck Pearl Harbor), the Yokosuka D4Y "Judy" reconnaissance/dive bomber, and late-war variants of the Zero fighter (A6M8 with Kinsei 62).
• Mitsubishi Kasei (火星, Mars): A larger 14-cylinder twin-row radial producing 1,530-1,850 hp. It was the powerplant for the Mitsubishi G4M "Betty" twin-engine bomber — the Navy's primary land-based medium bomber — as well as the Mitsubishi J2M Raiden "Jack" interceptor.
• Mitsubishi Zuisei (瑞星, Auspicious Star): A 14-cylinder twin-row radial producing 875-1,080 hp. A total of 12,795 were manufactured. It powered early Zero fighter variants (A6M1 prototype) and the Mitsubishi C5M reconnaissance aircraft.
• Mitsubishi Ha-43 / MK9: An advanced 18-cylinder twin-row radial intended to power next-generation fighters like the Mitsubishi A7M Reppu. Production was severely disrupted by the bombing campaign before significant numbers could be completed.

The factory's output represented over 40% of Japan's total aircraft engine production, making it an irreplaceable strategic asset.

Student Mobilization (学徒動員)

As wartime labor shortages intensified, thousands of students were mobilized to work at the Daiko Plant. By June 1944, some 2,158 students from various schools were assigned to the factory, including students from Toho Commercial School (東邦商業, 439 students), Aichi Middle School, and other institutions. Students as young as 14-15 years old worked in deep-night shifts assembling precision engine components. On June 22, 1944, Toho Commercial School students became the first in Aichi Prefecture to be assigned to full overnight factory shifts.

The Bombing Campaign (1944-1945)

The Daiko Plant's critical importance made it one of the highest-priority targets for the US Army Air Forces' XXI Bomber Command. The plant was subjected to seven precision bombing raids between December 1944 and April 1945:

1. December 13, 1944: The first and most devastating raid. Approximately 90 B-29 Superfortresses from the Mariana Islands attacked at around 1:00 PM from altitudes of 8,050-9,850 meters, dropping 181 tons of bombs. Around 40 buildings were totally or partially destroyed. The death toll was approximately 330 people, including factory workers, Women's Volunteer Corps (女子挺身隊) members, and mobilized students. At Toho Commercial School alone, 20 people were killed — 2 teachers and 18 students, mostly 4th-year students (19th graduating class) who had been on deep-night shift duty.

2. December 22, 1944: Second raid continuing the systematic destruction.

3. January 23, 1945: Third raid.

4. February 15, 1945: Fourth raid.

5. March 24, 1945: Fifth raid.

6. March 30, 1945: Sixth raid.

7. April 7, 1945: Final raid, completing the destruction of the facility.

Over the course of these seven raids, more than 600 B-29 sorties dropped over 1,700 tons of high-explosive bombs and incendiary weapons on the plant. The cumulative death toll exceeded 2,600 people — factory workers, civilian employees, mobilized students, and local residents. Post-war US Strategic Bombing Survey maps confirmed the plant was "completely destroyed."

The destruction of the Daiko Plant had catastrophic consequences for Japan's war effort. With over 40% of the nation's aero-engine production capacity eliminated, aircraft factories across the country — including the Oe Plant producing Zero airframes — found themselves without engines to install. This single industrial loss contributed significantly to the collapse of Japanese air power in the final months of the war.

Post-War Legacy

After the war, portions of the Daiko site continued to be used by Mitsubishi Heavy Industries for industrial purposes. In 1986, Mitsubishi's remaining operations at Daiko were fully relocated to Komaki. Construction of the Nagoya Dome baseball stadium began on August 8, 1994 on the former factory grounds, and the dome opened on March 12, 1997 (now known as Vantelin Dome Nagoya). The Nagoya University Daiko Medical Center is also located in the vicinity of the former plant site.

Today, little physical trace remains of the massive engine works. Memorial services are held periodically to honor the workers and students who perished in the bombings. The Peace Aichi museum (ピースあいち) in Meitō Ward preserves historical materials documenting the factory's history and the devastating air raids.