Former Army Ministry Site (Ichigaya Heights)

The former Army Ministry (陸軍省, Rikugun-shō) occupied a commanding position atop Ichigaya Heights (市ヶ谷台) in what is now Shinjuku Ward, Tokyo. Established in April 1872 as part of the Meiji government's modernization of Japan's military, the Army Ministry was the cabinet-level organ responsible for the administration, personnel, logistics, and budget of the Imperial Japanese Army (IJA). The site at Ichigaya had served as a military installation since the early Meiji era, when the Imperial Japanese Army Academy (陸軍士官学校) was opened there in 1874 on the former Owari-Tokugawa feudal estate.

As Japan's military ambitions expanded through the 1930s and into full-scale war, the Ichigaya compound grew into the most important military command complex in the empire. From December 1941, when the Army's central organs moved from Miyakezaka into the buildings vacated by the Army academies, the site housed three critical organizations: the Army Ministry (陸軍省), responsible for army administration under the War Minister; the Army General Staff Office (参謀本部, Sanbō Honbu), which directed strategic and operational planning; and the Imperial General Headquarters Army Section (大本営陸軍部, Daihon'ei Rikugunbu), the supreme wartime command authority reporting directly to the Emperor. From these offices, Japan's military leaders planned and directed operations across the vast Pacific and Asian theaters of war.

The compound's most dramatic moment came on the night of August 14–15, 1945, during the Kyūjō Incident (宮城事件, also known as the Palace Incident). After the Supreme War Council accepted the Potsdam Declaration and Emperor Hirohito decided to surrender, a group of mid-ranking army officers led by Major Kenji Hatanaka launched a desperate coup attempt. The conspirators assassinated Lieutenant General Takeshi Mori, commander of the Imperial Guard Division, at the Guard Division headquarters and forged orders to seal the Imperial Palace. Officers at the Army Ministry, particularly War Minister Korechika Anami, played pivotal roles — Anami refused to support the coup, and committed ritual suicide (seppuku) in the early hours of August 15. The plotters also searched the NHK broadcasting station and the Imperial Household Ministry attempting to find and destroy the Emperor's pre-recorded surrender announcement (玉音盤). The coup collapsed by morning when Eastern Army District Commander General Shizuichi Tanaka refused to join and ordered the rebels to stand down. The surrender broadcast proceeded at noon on August 15, 1945.

After Japan's defeat, the Allied occupation forces took over the Ichigaya compound. The main building (一号館) was used for the International Military Tribunal for the Far East (Tokyo Trials, 1946–1948). After its return to Japan, the compound became JGSDF Camp Ichigaya, housing the Eastern Army headquarters from 1960, and in May 2000 the Japan Defense Agency moved there. In the course of that redevelopment, Building No. 1 — built in 1937 as the Army Academy headquarters and used by the Army Ministry during the war — was demolished, though its historically significant sections were relocated and reconstructed within the compound as the Ichigaya Memorial Hall (市ヶ谷記念館). Today, the entire compound serves as the headquarters of the Ministry of Defense (防衛省), and its grounds encompass the site where the Army Ministry once stood. While no original Army Ministry structures remain in situ, the location itself — atop the distinctive Ichigaya Heights — continues to serve as Japan's foremost military-administrative center, a continuity spanning over 150 years.