Despite her mediocre photographic credentials, during World War II Chapelle managed to become a war correspondent photojournalist for National Geographic, and with one of her first assignments, was posted with the Marines during the battle of Iwo Jima. She covered the battle of Okinawa as well.
After the war, she traveled all around the world, often going to extraordinary lengths to cover a story in any war zone. During the Hungarian Revolution of 1956, Chapelle was captured and jailed for over seven weeks. She later learned to jump with paratroopers, and usually travelled with troops. This led to frequent awards, and earned the respect of both the military and journalistic community. Chapelle was a tiny woman known for her refusal to kowtow to authority and her signature uniform: fatigues, an Australian bush hat, dramatic Harlequin glasses, and pearl earrings.
Despite early support for Fidel Castro, Dickey was an outspoken anti-Communist, and loudly expressed these views at the beginning of the Vietnam War. Her stories in the early 1960s extolled the American military advisors who were already fighting and dying in South Vietnam, and the Sea Swallows, the anticommunist militia led by Father Nguyen Lac Hoa.
Chapelle was killed in Vietnam on November 4, 1965, when on patrol with a Marine platoon, the lieutenant in front of her kicked a tripwire boobytrap, consisting of a mortar shell with a hand grenade attached to the top of it. Chapelle was hit in the neck by a piece of shrapnel and died soon after.
Her last moments were captured in a photograph by Henri Huet. Her body was repatriated with an honor guard consisting of six Marines and she was given full Marine burial. She became the first female war correspondent to be killed in Vietnam, as well as the first American female reporter to be killed in action.