In August 1945, a Japanese newspaper sent a photographer from Tokyo to two cities that the United States military had just leveled with atomic bombs.

The photographer, Eiichi Matsumoto, had covered the firebombings of other Japanese cities. But the scale of the calamity that he encountered in Hiroshima and Nagasaki, he later recalled, was on another level.

At a Red Cross hospital near Hiroshima’s ground zero, he met victims dotted with red spots, a sign of radiation sickness. And on the desolate, rubble-strewn streets of Nagasaki, he watched families cremating loved ones in open-air fires.

“I beg you to allow me to take pictures of your utmost sufferings,” Mr. Matsumoto, who was 30 at the time, said he told survivors. “I am determined to let people in this world know without speaking a word what kind of apocalyptic tragedies you have gone through.”

Mr. Matsumoto, a photojournalist for the Asahi Shimbun newspaper who died in 2004, is among dozens of photographers who bore witness after the bombings, which forced Japan’s surrender and ended World War II.

Some of their images, banned until the American occupation ended in 1952, were eventually exhibited in museums and other venues across Japan. They also became fodder for antinuclear activists waging nonprofileration campaigns.

But in the United States, the photographs are still virtually unknown.

“Americans, when they think about atomic war, think about the mushroom cloud,” said Benjamin Wright, a doctoral student at the University of Texas at Austin who helped curate “Flash of Light, Wall of Fire,” a new book of photographs about the 1945 bombings.

“Perhaps they think of a destroyed city, but it’s very much a bird’s-eye view,” Mr. Wright said by telephone.

The book, published this month by the University of Texas Press to commemorate the 75th anniversary of the bombings, attempts to change that. It includes images from more than a dozen Japanese photographers, starting with Mr. Matsumoto’s photo of a Hiroshima wall clock that stopped at the moment when a nuclear bomb detonated above the city in a flash of light.