It was essentially a home guard and garrison, responsible for civil defense, anti-aircraft defenses, and for organizing guerrilla warfare cells in anticipation of the projected Allied invasion of the Japanese home islands in Operation Downfall (or Operation Ketsugō (決号作戦, Ketsugō sakusen) in Japanese terminology).
Although its territory encompassed all of western Japan, its primary mission was to ensure the security of southern Kyūshū, which was regarded as the most probable target for invasion.
Its forces consisted mostly of poorly trained reservists, conscripted students and home guard militia.
When the atomic bomb was dropped on Hiroshima, most of the military units, logistical arms, and command staff of the Second General Army were killed.
Elements remained in place under the American occupation authorities until November 1945 to assist with the demobilization of Japanese troops.