WASHINGTON — The Navy Annex was never intended to last long or, for that matter, to house human beings. The 1-million-square-foot complex, perched on a hill in Arlington County, Virginia, overlooking the Pentagon, was designed as a temporary warehouse but pressed by wartime needs into service as offices for the Navy and Marine Corps.

Seven decades later, including more than 50 years as Marine Corps headquarters, the Navy Annex is coming down. Demolition crews are gutting the interior and, late last month, began tearing down its exterior walls. The 42-acre site is to be turned over to neighboring Arlington National Cemetery for grave sites.