PARIS — In the year after the United States’ invasion of Iraq, a 22-year-old pizza delivery man here couldn’t take it anymore. Sickened by images of American soldiers humiliating Muslims at the Abu Ghraib prison, he made plans to go fight United States forces. He studied a virtual AK-47 on a website. Then he took lessons from a man, using a hand-drawn picture of a gun.

It was an almost laughable attempt at jihad, and as the day of his departure approached, the delivery man, Chérif Kouachi, felt increasingly unsure of himself.

When the police arrested him hours before his 6:45 a.m. Alitalia flight on Jan. 25, 2005, he was relieved. “Several times, I felt like pulling out. I didn’t want to die there,” he later told investigators. “I told myself that if I chickened out, they would call me a coward, so I decided to go anyway, despite the reservations I had.”

A decade later, Chérif Kouachi, flanked by his older brother Saïd, 34, no longer had any reservations, as the two jihadists in black, sheathed in body armor, gave a global audience a ruthless demonstration in terrorism.