1st prize in the People Observed Portraits Stories category. Carla Kogelman, the Netherlands. The photo shows Hannah and Alena, two sisters living in the rural village of Merkenbrechts, Austria. (Photo by Carla Kogelman/World Press Photo)

In the spring of 1965, within weeks of 3,500 American Marines arriving in Vietnam, a 39-year-old Briton named Larry Burrows began work on a feature for LIFE magazine, chronicling the day-to-day experience of U.S. troops on the ground – and in the air – in the midst of the rapidly widening war. The photographs in this gallery focus on a calamitous March 31, 1965, helicopter mission; Burrows’ “report from Da Nang”, featuring his pictures and his personal account of the harrowing operation, was published two weeks later as a now-famous cover story in the April 16, 1965, issue of LIFE.

Photo: Man your battle stations: The crew chief of helicopter Yankee Papa 13, lance corporal James C. Farley, mans an M-60 machine gun during a mission near Da Nang, Vietnam on March 31, 1965. (Photo by Larry Burrows/Time & Life Pictures)

Gunfire erupted at a Denver pot celebration Saturday, injuring two people and scattering a crowd of thousands who had gathered for the first 4/20 counterculture holiday since the state legalized marijuana... Photo: A woman smokes a large marijuana joint at the Vancouver Art Gallery during the annual 4/20 day, which promotes the use of marijuana, in Vancouver, British Columbia April 20, 2013. (Photo by Ben Nelms/Reuters)

Three prostitutes lean out of a window in Santiago, Chile, in an attempt to entice customers inside, circa 1950. (Photo by Three Lions/Getty Images)

Three Chinese soldiers at the time of a civil war in China. (Photo by General Photographic Agency/Getty Images). 1922

A woman walks past servicemen of the self-proclaimed Donetsk People's Republic (DNR), who take part in a rehearsal for the Victory Day parade in Donetsk, Ukraine on May 3, 2018. (Photo by Alexander Ermochenko/Reuters)

A cosplayer poses for a photograph during the Tokyo Rainbow Pride Parade on May 6, 2018 in Tokyo, Japan. The LGBT community and supporters marched down Shibuya and Harajuku areas on the final day of the Tokyo Rainbow Pride 2018 event. (Photo by Tomohiro Ohsumi/Getty Images)

Lizzy Huggler, 20 ,wears blue ties on her legs on the third day of the Firefly Music Festival in Dover, Delaware U.S., June 16, 2018. (Photo by Mark Makela/Reuters)