Tokyo Second Army Arsenal (Itabashi Powder Works)

The Tokyo Second Army Arsenal Itabashi Plant (東京第二陸軍造兵廠板橋製造所) traces its origins to 1876 (Meiji 9), when the Meiji government established a gunpowder factory on the former lower residence of the Kaga Domain's Maeda clan in Itabashi. Strategically utilizing the hydraulic power of the Shakujii River, it was the first gunpowder manufacturing plant established by the Meiji government.

The facility evolved through several organizational changes. Initially called the Artillery Headquarters Itabashi Sub-factory (砲兵本廠板橋属廠), it was reorganized as the Tokyo Artillery Arsenal Itabashi Gunpowder Factory in 1879, then became part of the Tokyo Second Army Arsenal in 1940. At its wartime peak, the complex employed over 7,000 workers and was a critical node in Japan's military-industrial supply chain, manufacturing smokeless powder, explosives, and ammunition components for the Imperial Japanese Army.

The Army Gunpowder Research Institute (陸軍火薬研究所), established on the grounds in 1899, conducted cutting-edge research on propellants and explosives. Its facilities included brick-constructed materials testing laboratories, reinforced-concrete combustion experiment chambers, and ballistic testing tunnels (弾道検査管) where ammunition performance was verified under actual firing conditions. An open-air firing range with earthen embankments completed the testing complex.

As the war situation deteriorated, the Fukaya plant in Saitama Prefecture was opened in October 1944 as an evacuation site for the Itabashi works. After Japan's surrender, the site was partially used by the U.S. military as the Tokyo Ordnance Supply Depot before being returned and redeveloped. Much of the land was sold to private entities, with Tokyo Kasei University establishing its Itabashi campus on part of the former arsenal grounds.

In October 2017, the "Army Itabashi Gunpowder Manufacturing Plant Ruins" (陸軍板橋火薬製造所跡) was designated a National Historic Site of Japan. Key surviving structures include the Belgian-made hydraulic grinding wheel monument (圧磨機圧輪記念碑) at Kaga West Park, brick laboratory buildings, ballistic testing tunnels, and firing range earthworks. Itabashi Ward is developing the site as a historic park (the ward now targets a full opening in fiscal 2029) to preserve and interpret this important chapter of Japan's military-industrial heritage.