War photographs have been informing and disturbing the public for well over a century. In her book "Shooting War: Photography and the American Experience of Combat" (Basic Books), Susan D. Moeller cites the contributions made by photography and the questions raised by its content since the Spanish-American War in 1898.

"Photography," Moeller writes, "makes war accessible." It tells a brief story about one event. The "photo history of combat is key to understanding the American perception of war."In this case "perception" cuts two ways.

First, public and personal opinion will influence the way a photographer approaches a subject. Is the combat seen as necessary and heroic? Is the mission seen as an intrusion or a needless sacrifice? Attitude can determine, for instance, whether a photographer shoots from below, making a soldier appear tall and gallant, or chooses to look down on a weary infantryman covered with mud.

Second, once the picture is published, it can reinforce the viewers' existing ideas about the conflict. (It is much harder for a single photograph to change public opinion - as the majority view shifts, so will the press.)

Because of the nearly simultaneous advent of the halftone, which allowed pictures to be printed alongside letterpress, the Spanish-American War was the first to be extensively covered photographically in newspapers. The proximity of Cuba to the States also made it possible, in the days before the wire services, for glass negatives to be brought back on hired boats.

The importance of photography to civilian news and military strategy was recognized at once. (The fact that stirring photographs sold more newspapers was not lost on William Randolph Hearst and his competitors, either.)

The military appreciated the fact that the camera was much quicker and more accurate than drawings at showing enemy positions and terrain. While it was 1917 before the Signal Corps Photographic Section was established, men in the signal companies were equipped with cameras in the 1890s.

Moeller's book continues with a section for each major war of the 20th century: World Wars I and II, Korea and Vietnam. In each part, she establishes the context of the conflict and the major photographers working - often quoting them extensively - and then discusses the photographs themselves. This is not a picture book, but one of the few serious, in-depth attempts to understand the significance of the most powerful medium of the century.

War coverage is photography at its most intense. Photographers are pushed to perform through physical extremes - the ice cold of Korea and the leech-infested waters of Vietnam - to say nothing of the danger of being killed. Photographers are not onlookers from a safe distance, but are increasingly on the inside of the battle. From there, they must get film and accurate captions out, by wire transmission or mail, if the public is to see the pictures.

The shortcomings of war photography are the shortcomings of photography itself. Moeller points out that the story told by war photographs "is not the only story that can be told." In other words, every photograph is one photographer's view of one moment out of a continuing narrative. A good photographer will try, of course, to sum up an event fairly. But capturing the essence of a war, a battle or a skirmish in one photograph is not an easy task.

Photographers often shoot details to tell a larger story: terror on the face of villagers, a family's joy at the homecoming of a soldier, or the determination on the face of a general. Each imparts a glimpse of the truth about war.

Great war photographers and their photographs piece together the story for us.