Sagami Army Arsenal Ruins

The Sagami Army Arsenal (相模陸軍造兵廠, Sagami Rikugun Zōheishō) was established in 1938 as the "Army Arsenal Tokyo Works Sagami Weapons Manufacturing Plant" in the villages of Ōno and Aihara in Kōza District, Kanagawa Prefecture (present-day Chūō Ward, Sagamihara City). In 1940, it was elevated to full arsenal status and redesignated the Sagami Army Arsenal. The facility was part of the Imperial Japanese Army's strategic buildup in the Sagamihara area, which was developed as a "military capital" (軍都) during the 1930s and 1940s.

The arsenal's primary mission was the manufacture and assembly of tanks and armored fighting vehicles for the Imperial Japanese Army. Its two main production divisions handled tank manufacturing and ammunition production respectively. Key products included the Type 97 Chi-Ha medium tank — with a target monthly output of 20 units, though actual production never exceeded 15 — and the Type 4 Chi-To medium tank. The facility also served as the test bed for the experimental 120-ton O-I super-heavy tank, one of the most ambitious armored vehicle projects of the war. Additionally, the arsenal produced fire balloon (風船爆弾) incendiary devices that were launched from Chiba toward the American West Coast.

At its wartime peak, the Sagami Arsenal is reported to have employed approximately 30,000 workers, with roughly 80 percent consisting of conscripted laborers, young trainees, members of the Women's Volunteer Corps, and mobilized students. A dedicated tank test course called the "Tank Vehicle Operation Test Field" (戦車類運行試験場) was laid out across the Tama Hills, with a planned circuit of approximately 30 kilometers. About 8 kilometers were completed in 1943, allowing tank driving tests and operator training to be conducted.

In September 1945, following Japan's surrender, the U.S. Army 5th Cavalry Regiment occupied the arsenal. In 1949, the facility was formally requisitioned and became the "U.S. Army Yokohama Engineering Depot Sagami Plant," initially focused on repairing weapons and military vehicles. In 1961, it was merged with the Sagami Warehouse District to form the Sagami General Depot (相模総合補給廠), which continues to operate as a major U.S. Army logistics and supply installation.

Today, while the core of the former arsenal remains within the fenced perimeter of the U.S. military base, portions of the surrounding area preserve traces of the wartime facility. The former tank test course, long known as the "Tank Road" (戦車道路), survives as the Ridge Greenway (尾根緑道) in neighboring Machida, Tokyo. Parts of the arsenal's railway spur line (引込線) can still be traced in the urban landscape. In recent years, portions of the depot land have been returned to Japan, with plans for parks and urban redevelopment that acknowledge the site's military heritage.