‘The bomber will always get through,” Stanley Baldwin told Britain’s House of Commons in 1932. “The only defense is in offense, which means that you have to kill more women and children more quickly than the enemy if you want to save yourselves.” Baldwin was no warmonger. His purpose was to underscore the indiscriminate horror likely to come from the air in an era of big military airplanes carrying large payloads of explosives. His declaration reflected the thinking of theorists ranging from the Italian general Giulio Douhet to the popular novelist H.G. Wells. It also acknowledged the truism that wars are ultimately between peoples and societies, not just armed forces.

War came within a few short years, and the bomber was its most feared weapon. In Europe, Germany showed the way—first in Spain with Guernica, then in Britain with the Blitz against London, Coventry, Hull and other cities. Revenge followed in the form of British and American bombers plastering German population centers with equal indiscrimination. Japanese bombers killed or wounded thousands of Chinese at Shanghai in 1932 and wreaked havoc at Pearl Harbor in December 1941.

In late 1944, Japan began to be attacked by the most formidable of the World War II bombers, the American B-29. Japan’s defenses were weak and its provisions for civilian shelters grossly inadequate. Its wood-and-paper buildings were terribly vulnerable to incendiary bombs. Few had basements to which their inhabitants could retreat. On the night of March 9, 1945, more than 300 American B-29s raided a working-class area of Tokyo that was laced with small factories. The incendiary bombs set off firestorms that laid waste to nearly 16 square miles of the city and killed approximately 100,000 civilians and left the survivors demoralized.

Other Japanese cities endured ordeals similar to Tokyo’s. Two, however, were relatively untouched—Hiroshima and Nagasaki. Their inhabitants never realized that they were being saved for a terrible new weapon. The reprieve came to an end on Aug. 6 and Aug. 9, 1945, in each case with single atomic bombs that probably produced fewer deaths than the Tokyo firebombing but spread greater fear.

Charles Pellegrino’s study of Hiroshima, “To Hell and Back,” and Susan Southard’s “Nagasaki” give scant attention to the larger military and diplomatic issues of the atomic bombings. Instead they recount the ordeals of ordinary and altogether sympathetic citizens coping with a sudden, devastating event that destroyed the world they had known. The lucky were killed instantly, some simply vaporized. Others displayed mute testimony to the event. Mr. Pellegrino describes one such example, drawn from the account of a survivor: “A statue, standing undamaged, . . . was in fact a naked man. . . . The man had become charcoal—a pillar of charcoal so light and brittle that whole sections of him crumbled at the slightest touch.” Another survivor, we are told, gathers the bones of a young woman, resolves to return them to her parents and manages to catch the last train to their home—in Nagasaki.

Ms. Southard gives us similar stories and provides photographs of aged Japanese still bearing horrible physical scars from their burns. She notes that the scars could also be psychological—feelings of “bitterness and outrage,” the mockery that could come with disfigurement. For some, she writes, the “fear of illness and death never ceased.” Both authors describe the harrowing effects of radiation sickness.

The maimed survivors of each city devoted much of their lives to evangelizing against the bomb. It is easy to write off such narratives as exercises in victimology, but it is also important to understand the effects of nuclear weapons in an age when they have become vastly more powerful and have been developed by nations of dubious responsibility.

What is missing from both books is context. Neither author properly discusses the factors that went into the American decision to use the bomb. Nor do they venture an opinion on whether the bomb shortened the war. They focus on the ways the bomb affected civilians who had to cope with a catastrophe.

“To Hell and Back,” one may remember, appeared in an earlier form, in 2010, as “The Last Train From Hiroshima.” The publication of that book was suspended when the authenticity of one of Mr. Pellegrino’s sources—a man who claimed to have been on a plane accompanying the Enola Gay bomber on its Hiroshima mission—was called into question. That source and his assertions are gone from the new book. A foreword notes that he had indeed “tricked” the author, who later admitted his mistake.

In a preface to “To Hell and Back,” Mark Selden, a scholar of East Asian studies, declares that Mr. Pellegrino’s narrative “encourages us to reflect anew on the ethics and horrifying outcome of World War II strategies of massive civilian bombing, whether by Germany, Japan, or England, or by American fire-bombing of German and Japanese cities and the atomic bombing of Hiroshima and Nagasaki.”

His statement reminds us that the atomic bombs were the logical outcome of a style of war taken for granted on both sides by the summer of 1945. Britain suffered heavy bombing and massive property destruction, but civilian deaths for the nation were less than 45,000. The port city of Hull (population, 320,000), roughly analogous to Hiroshima or Nagasaki, endured damage to an estimated 95% of its housing stock but lost only 1,200 civilians. Unlike Britain, Japan seems to have made little or no provision for the protection of its civilian population.

Were the bombs necessary to compel surrender? U.S. policy—laid down by Franklin Roosevelt, followed by Harry Truman and supported by most Americans—was uncompromising. The U.S. would accept only unconditional surrender, to be followed by military occupation.

In Japan, advocates of a last-ditch resistance could not promise victory but could guarantee heavy casualties for the invaders. The last battle of the war—Okinawa—made the point. Okinawa was a small island, and the U.S. possessed overwhelming ground, naval and air superiority. Even so, the battle raged from April 1 to June 21, 1945, with 92,000 Japanese troops fighting to the death and kamikaze planes inflicting significant damage on the offshore American fleet. U.S. casualties (killed and wounded) were approximately 45,000.

The experience made an impression in Washington. The Japanese home islands were next. Japan’s leaders made no secret of their plans to wage a dogged resistance that would mobilize the civilian population, right down to teenagers armed only with clubs and sticks; and the leaders clung to the fantasy of a negotiated peace brokered by the still-neutral Soviet Union. They rebuked their ambassador in Moscow for telling them that the Russians, who were moving troops to attack Japan in East Asia, would be of no help.

American military planners focused on the southernmost Japanese home island of Kyushu as a first target, to be followed by an invasion of the island of Honshu and a final campaign across the Tokyo plain in 1946. Meeting with his military chiefs in Washington on June 18, 1945, President Truman expressed his hope of “preventing an Okinawa from one end of Japan to the other.” A month later, the first atomic bomb was tested in the New Mexico desert. Hiroshima and Nagasaki quickly followed.

Critics of the atomic bombings often assert that Japan was “ready to surrender.” Clearly this was not the case. Japan could still muster formidable military resources. It is unlikely that resistance would have ever gotten down to teenagers armed with clubs and sticks but probable that an amphibious invasion of Kyushu would have exacted a price reminiscent of Okinawa. That possibility was unthinkable to most Americans.

Why did the Hiroshima and Nagasaki bombs compel surrender? Radiation effects aside—which were not always immediately evident—the bombs did no more damage than the conventional fire bombing of Tokyo, which had failed to produce any serious thought of a Japanese surrender. A big part of the answer has to be the shock value—a single bomb destroying a whole city.

The nuclear weapons of today make the ones detonated in 1945 look like firecrackers, and more and more countries possess them or threaten to do so. The editors of the Bulletin of Atomic Scientists picture a doomsday clock at three minutes to midnight. The virtue of these books is their reminder of just how horrible nuclear weapons are.