U.S. President Barack Obama reworked his historic Hiroshima speech many times as he prepared to deliver it last Friday, hoping to make it both "profoundly realist" and "idealistic," a top aide said.

Ben Rhodes, the deputy national security adviser and top speechwriter for the president, wrote in his personal blog that, as the first American president to pay respects in Hiroshima since the atomic bombing of the city on Aug. 6, 1945, Obama worked hard to make sure his speech would be "a broad reflection on what we must learn from history."

"Over the course of our trip, the President continually reworked his speech, consistently making a broader reflection on what we must learn from history," Rhodes wrote, "and combining a profoundly realist message about mankind's impulse towards conflict with an idealistic call for nations — and peoples — to see beyond their differences to the 'radical and necessary notion that we are part of a single human family.' "