President Barack Obama's visit to Hiroshima last year wasn't the source of controversy over the world's first nuclear attack so much as a reflection of the fact that this controversy never really goes away.

No sitting president had ever visited this city, destroyed by an atomic bomb on Aug. 6, 1945, in one of World War II's final acts. The visit was a lightning rod for strong opinions on both sides of the enduring question of whether using such a weapon in this way constituted a necessary step to end the war and avert even greater casualties — or a needless and disproportionate war crime, possibly amounting to genocide.

The nonprofit Atomic Heritage Foundation has neatly summed up the major points, adding that "the debate over the bomb continues to this day."

But if you're looking for some late-summer reading, a deeper dive into the details can be quite rewarding. Two respected historians, among many, who believe the decision to drop atomic bombs on Japan was a necessary one are Richard B. Frank, author of "Downfall: The End of the Imperial Japanese Empire" and D.M. Giangreco, whose 2010 volume "Hell to Pay: Operation DOWNFALL and the Invasion of Japan, 1945-1947" cites declassified documents from both U.S. and Japanese archives to make a compelling case.

They are opposed by, among others, revisionist historian John Ray Skates, whose 1994 book "The Invasion of Japan: Alternative to the Bomb" argues that Japan was a defeated nation and ripe for surrender.

Washington Post