President Barack Obama’s unprecedented 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 the final moves of World War II. The visit was a lightning rod for strong opinions on both side 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 neatly sums up the major points of this debate here.

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” (Penguin Books, 1999) and D.M. Giangreco, whose 2010 volume “Hell to Pay: Operation DOWNFALL and the Invasion of Japan, 1945-1947” (Naval Institute Press) cites declassified documents from both American 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” (University of South Carolina Press) turns the argument that Japan was a defeated nation, ripe for surrender, into a brisk and convincing read.

These books put you in the rooms where the critical decisions on both sides of World War II’s last acts were made and bring the men who made those decisions to life. And speaking of bringing history to life, they also afford you an excellent perspective for your next visit to the Smithsonian National Air and Space Museum’s Steven F. Udvar-Hazy Center, where the Enola Gay — the aircraft that actually delivered the Hiroshima bomb 72 years ago Sunday — stands on display.

Read more:

In Hiroshima 71 years after first atomic strike, Obama calls for end of nuclear weapons

Hear from survivors of the atomic bombing of Hiroshima