What does the excerpt suggest is the most contentious legacy of the atomic bombings in Japan?

Margaret MacMillan in her detailed study on wartime decisions reflects on the atomic bombings of Hiroshima and Nagasaki with a critical perspective. She notes that the bombings inflicted enormous civilian casualties and unprecedented destruction. The historian describes the event as a morally ambiguous act that has sparked debate among scholars and political figures alike. Her analysis emphasizes that the bombings accelerated the end of the war in the Pacific, yet at a controversial human cost. She contends that these actions have since become a focal point for discussions on the ethics of warfare. According to MacMillan, the bombings remain emblematic of the complex interplay between military necessity and moral considerations.

• Margaret MacMillan, Shadows of War, 2007