Obama's language was in many ways similar to the words he used in the wake of a mass shooting in Newtown, Conn., last winter and was aimed at stirring a nation's collective conscience to action.
So far, however, there is scant evidence that the American public or Congress have been swayed by the graphic videos, which were recorded in the neighborhoods near Damascus where the Aug. 21 attacks were allegedly carried out.
The administration has struggled to make the case that the alleged use of chemical weapons by Syrian President Bashar al-Assad on his own people has constituted such a horrifying escalation of the country's civil war that a U.S. military intervention is required.
In a Washington Post/ABC News poll last week, 64 percent opposed U.S. military action in Syria.
There are many reasons why the public and lawmakers may be unprepared to support a U.S. attack on Syrian targets, including war fatigue after Afghanistan and Iraq and a lack of clarity from the administration about its goals. But some experts said another factor might be at play: The images, while gruesome and disturbing, do not immediately produce a clear narrative.
Images of dead bodies or men gasping for air and convulsing may produce a horrified reaction, but they do not necessarily explain to a viewer what happened or why, said Scott Sigmund Gartner, a scholar at Penn State University who has studied the effect of war imagery on the public.
Obama, briefed daily by his national security team, "sees the photos and is essentially writing his own captions," Gartner added. "The public sees them without his feeling of responsibility."
Charles Blair, of the Federation of American Scientists, said humans are "hard-wired" to be frightened by poisons and gases. But on Syria, he said, the videos lack raw emotional power compared to bloodier photos and videos that the public has seen from other war zones.
During the creation of the atomic bomb, Blair said, scientists watching a test blast in the desert "were uninspired by it. It was not as large as they thought, and people were underwhelmed by the power. They were a faraway series of blasts. This is sort of the same thing."
Richard Price, a professor of political science at the University of British Columbia, is the author of "The Chemical Weapons Taboo," which traces the history of chemical weapons from World War I through Nazi concentration camps and to an international agreement forbidding such weapons in 1997.
In his study, Price found that contrary to conventional wisdom, people did not immediately have a more visceral reaction to the damage inflicted by chemical weapons than from others.
"It's not that people do not have a reaction to the horror, they do," Price said. "But is it any different from other forms of mass casualties?"