Former Second General Army Headquarters

The Second General Army (第二総軍, Dai-ni Sōgun) was one of two army groups created by Imperial General Headquarters in the final months of World War II to organize the defense of the Japanese home islands against the expected Allied invasion, known as Operation Downfall. Established on April 8, 1945, the Second General Army was headquartered in Hiroshima and assigned responsibility for the defense of western Honshū (west of the Suzuka Mountains), Shikoku, and Kyūshū — the areas most likely to face an Allied amphibious assault.

The command was placed under Field Marshal Hata Shunroku, one of Japan's most senior military leaders who had previously served as War Minister and commander of the China Expeditionary Army. His chief of staff was initially Lieutenant General Tadakazu Wakamatsu, succeeded by Lieutenant General Seisaburo Okazaki in July 1945. The Second General Army's primary mission under Operation Ketsu-Go (決号作戦) was to prepare civil defense measures, organize anti-aircraft defenses, and establish guerrilla warfare cells across western Japan, with particular emphasis on southern Kyūshū — identified as the most probable Allied landing zone.

The headquarters was initially established at the former Fifth Cavalry Regiment barracks near Futaba-no-sato in Hiroshima's eastern district, beside the East Parade Ground at the foot of Mount Futaba, east of the military complex centered on Hiroshima Castle. Hiroshima had served as Japan's premier military city since the Sino-Japanese War of 1894-95, when Emperor Meiji established his Imperial General Headquarters within the castle grounds. By 1945, Hiroshima hosted a dense concentration of military facilities including the Chūgoku Military District headquarters, the 59th Army, and numerous support units.

On the morning of August 6, 1945, the atomic bomb "Little Boy" detonated over Hiroshima at 8:15 AM. The blast devastated the military district, and the Second General Army's headquarters and subordinate organizations suffered catastrophic losses. By some estimates as many as 20,000 Japanese military personnel in the city perished, including soldiers of the Second General Army, the Chūgoku Military District, and the Fifty-Ninth Army. Lieutenant Colonel Prince Yi U (李鍝), a member of the Korean royal family serving as a staff officer, was caught by the blast near the Fukuya department store while riding to headquarters and died the following day on Ninoshima; he was posthumously promoted to colonel. Field Marshal Hata himself survived, having been at his quarters slightly farther from the hypocenter. Surviving staff regrouped at Ujina port to organize emergency relief operations and attempt to maintain military order in the devastated city.

Today, the former military grounds within and around Hiroshima Castle have been transformed into a public park. The reconstructed castle keep (rebuilt in 1958) houses a museum documenting Hiroshima's history as a military city. Memorial markers and informational plaques throughout the castle grounds note the locations of the various wartime military headquarters. The site stands as a powerful reminder of Hiroshima's dual identity — both as imperial Japan's foremost military command center and as the target of the world's first nuclear attack in warfare.