Americans had never seen anything like the photographs from the battlefield at Antietam. A critic for the New York Times said the unflinching images of the dead defied "the public's long nurtured belief that death on the battlefield was glorious and heroic."
Alexander Gardner's Civil War photos became iconic markers of sacrifice and suffering for later generations. But they had limited reach in their day. The vast majority of Americans could not make it to Mathew Brady's galleries in New York or Washington, where the pictures were shown, or afford the limited-edition books that published the photos.
In virtually every American war that has followed, including the ongoing combat in Iraq, journalists have captured stunning images from the heart of battle. Yet they have often struggled with whether to take, or publish, photos of the dead and wounded.
By the time of the Spanish-American War, technology had advanced enough that photographers could ship pictures home. But most considered it disrespectful to take pictures of their dead countrymen.
In World War I and the early months of World War II, U.S. military censors blocked most photos of American losses. That meant few pictures of the dead or wounded. Even pictures of bombed-out tanks, jeeps and other equipment could be censored by military overseers, who believed such pictures would deflate morale on the home front, said University of Maryland journalism professor Susan Moeller, author of "Shooting War: Photography and the American Experience of Combat."
That practice changed dramatically in 1943, when President Franklin D. Roosevelt, the War Department and the Office of War Information decided Americans needed a less-sanitized view to understand the true risks and costs of the war, Moeller said.
After restrictions were lifted, pictures of the dead and wounded began to appear regularly. Life magazine published one of the first in September 1943 — a full-page photo by George Strock of the bodies of three U.S. soldiers at the edge of the surf on Buna Beach in New Guinea.
"Why print this picture, anyway, of three American boys dead upon an alien shore?" the magazine asked in an accompanying essay. "Is it to hurt people? To be morbid?"
"Those are not the reasons. The reason is that words are never enough."
Rather than turn off the public, the picture and others like it helped synthesize U.S. opinion in support of the war, Moeller said. It also helped usher in a new era of frank war photography, which many believe reached its apogee two decades later in Vietnam.
Photographers such as Larry Burrows, Henri Huet, Horst Faas and Philip Jones Griffiths found the U.S. military would fly them almost anywhere from Saigon, putting them quickly in the thick of the action. Unlike today's "embed" photographers in Iraq, they did not have to sign agreements with the military and they submitted to few rules.
The freedom — and the fact that some photographers spent years on assignment getting to know Vietnam — produced extraordinary photos such as Burrows' 25-picture Life magazine photo essay depicting a helicopter crew chief's ultimately failed attempt to save a fellow flier.
Photographers of that era enjoyed not only extraordinary access, but a prized, high-profile venue for their work. Life magazine then had a circulation of more than 7.2 million and a coffee-table readership that was much higher.
"There is no real equivalent today, because everyone read Life magazine," said Richard Pyle, a onetime Associated Press bureau chief in Saigon, who co-wrote a book about photography during the war. "Even a great photo can get lost today. We are awash in a marketplace of noise."
Still, Vietnam was far from a free-for-all of vivid photography. Then, as now, photographers said they felt the pull of loyalty to American troops and inhibitions about taking pictures of casualties, especially those that would identify the dead.
"I think the Stockholm syndrome does apply: You become part of the group and you don't want to let the group down," by taking negative photos, said Griffiths, whose book "Vietnam Inc." was cited by many as synthesizing the futility of the war.
It was not pictures of American GIs or U.S. casualties that became the iconic images of the Vietnam War. Instead, people remember photos of Vietnamese suffering: a Buddhist monk burning himself to death, a naked girl fleeing a napalm attack, and the head of South Vietnam's national police executing a Viet Cong prisoner with a shot to the head.
Television news also found little airtime for depictions of U.S. casualties in Vietnam, said Daniel C. Hallin, a UCSD communications professor who studied thousands of hours of newscasts on the war.
Later documentary and feature films focusing on the violence have contributed to the common misconception that those images were all readily available at the time. But Hallin said his research, described in the book "The Uncensored War," found that television provided "a very limited and sanitized portrayal" of the bloodshed, except during brief periods such as the 1968 Tet offensive.
Nonetheless, many blamed the media for undercutting support for the war. And that viewpoint would influence the Pentagon's handling of future wars.
When it invaded the Caribbean island of Grenada in 1983, the Reagan administration left reporters and photographers behind. That fueled a backlash and an agreement from the military in the 1991 Persian Gulf War to allow limited access to a pool of media representatives who would share their reports with other news outlets.
The arrangement allowed a minimal view of the fighting. But photographers protested their limited access and said military handlers held back some images until they were too old for publication.
America's charge through occupied Kuwait left little time for in-depth coverage. But David C. Turnley of the Detroit Free Press managed to take one of the war's most moving photos. It showed Sgt. Ken Kozakiewicz crying beside the body bag of a buddy who had just been killed by friendly fire.
As was common in that war, Turnley used a military courier to ship his film. But two days later he found it still hadn't been passed on to his editors. With the dead man's next of kin already notified, Turnley recalled, he appealed to an officer to release the film.
"I said, 'If you don't release this photo you are really contributing to the impression that soldiers over here didn't sacrifice and didn't risk their lives,' " Turnley recalled. "He released the film. And it ended up being published around the world."