Scenes from wars have evoked strong emotions going back to the American Civil War and the invention of photography. In Iraq, the most memorable images so far have been ones that induced pride or patriotism among most Americans, such as the fall of a dictator's statue in Baghdad, the dramatic rescue of Jessica Lynch, and the capture of Saddam Hussein.
But on Wednesday, for the first time in the year since the Iraq war and its aftermath began, Americans were shown gruesome scenes of four US civilians killed and put on display in Iraq.
Although the death toll was minor compared with suicide bombings in Iraq that have killed hundreds, the images and the visceral reaction to them are a reminder of how much the success of a war in this media age can depend on public support back home.
But such media events are mainly a test of a war's underlying reasons. They force a nation to rethink the sacrifices needed for a cause. If the reasons are thin and the sacrifices too high for the benefits of the cause, then the loss of public support can force the United States to cut and run.
That was the case in Vietnam after the images during the Tet Offensive in 1968 showed the US Embassy in Saigon under attack.
And again in Somalia during the 1993 incident in which dead US soldiers were dragged through the streets of Mogadishu.
But it hasn't been the case in most wars that the US has fought.
Thin reasons for military action, and not gruesome images, are what really end a war. For the Iraq invasion, President Bush laid out a multitude of reasons - from ending a potential terrorist threat from Saddam's weapons programs to creating a model Arab democracy. All of them were pitched as necessary to prevent another, or bigger, Sept. 11-type attack, either in the short term or in decades to come.
Over the months, polls have shown a steady but slim majority of Americans have backed this effort. And so far Democrats have offered only ways to improve the campaign in Iraq rather than calling for a withdrawal. Helping to counter this incident have been upbeat reports of US successes in rebuilding Iraq.
It's likely, then, that the Fallujah incident will result only in a change of tactics, such as beefed-up security for civilian workers, a faster pace toward creating an Iraqi military, more UN authority, a rebalance of power between Sunnis and Shiites, and so on.
The Bush administration's learn-as-it-goes approach in Iraq has needed such corrections. But its strategy is a long way from being toppled by media images.