For the warrior or the would-be rescuer -- the heroes -- there is no time to appreciate what one click of a camera shutter means to a suffering nation.
Six Marines still had an enemy to fight after they raised the American flag on Iwo Jima's Mount Suribachi. Three would die in that 1945 battle.
On Sept. 11, 2001, three New York City firefighters joined those who rushed to the World Trade Center to search for survivors who would never be found. Late that afternoon, they raised a small flag removed from a nearby boat. A monochromatic wall of gray debris soared in the background.
"There's no self-pity in that picture," said Capt. Patrick Burns, U.S. Navy liaison to New York, at the time.
The photographs of the flag-raisings at Iwo Jima and ground zero quickly became icons, moments in time that galvanized Americans who found new solidarity and unity.
And while the whereabouts of the Iwo Jima flag are known (it's at the National Museum of the Marine Corps), the fate of the World Trade Center site 3-foot-by-5-foot flag became a mystery.
CNN Films' "The Flag," which premieres Wednesday night on CNN, explores what may have happened to it.
It's a story replete with mystery.
Within hours of its raising, the flag disappeared from the World Trade Center site. The makers of the film documented this by looking at the background of photos taken soon after.
The flag that subsequently flew over Yankee Stadium as a patriotic rebuke to terrorism, and fluttered over the USS Roosevelt as the aircraft carrier sent missions over Afghanistan, was represented as the same flag that was raised.
The original flag was "either misplaced, stolen or secreted away by unknown forces in the chaos of ground zero," the film's directors said in a statement.
Raised flag became a national symbol
Dishonesty was not behind the story of the flag's travels, said Michael Tucker, who produced, wrote and directed "The Flag" with his wife, Petra Epperlein. There were more important things to do than keep up with a single flag, which was quickly joined by several others.
"(For) people who were down there, the most important thing for them was recovering people, even when they knew there were no survivors," Tucker said.
When an official was sent to pick up the flag a week or so later, he apparently received a larger flag, and it was flown at subsequent events.
"They had no reason to believe it wasn't the flag," Tucker said.
The story of the missing flag includes a larger, more philosophical question: Is it the actual flag that is most important -- or the ideals it represents?
For its part, the WTC flag photo -- taken by Tom Franklin of the Record newspaper in Bergen, New Jersey -- quickly became a symbol.
It was plastered on the cover of Newsweek, with the words, "God Bless America," and the image could be seen on everything from coffee cups to tattoos.
"Most people will see it happen once or twice in their lifetime -- where the whole nation stands together," said Tucker.
"It was the worst of times and probably the best of America," Tucker told CNN on Tuesday.
The makers of "The Flag" spoke with several photographers about going to ground zero and the heartbreaking scenes that awaited. The film is partly forensic, with an expert comparing photos of the original flag and others that appear to be larger.
Among those interviewed were the couple who owned the yacht from which the flag was taken by a firefighter to hang at the WTC site.
They wanted to donate the flag to the Smithsonian Institution and asked about a year after the attacks to borrow the signed flag briefly for a ceremony.
"When we got the flag, we were quite stunned that it was the wrong flag," said Shirley Dreifus. "... This wraps around the two of us, and we're not the thinnest people on Earth ... So we knew right away it was the wrong flag."