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)

A monarch butterfly rests on the ground at the Sierra Chincua butterfly sanctuary on a mountain in Angangeo, Michoacan November 24, 2016. Angangueo is a town and municipality located in far eastern Michoacán state in central Mexico noted for its history of mining and its location in the Monarch Butterfly Biosphere Reserve. The Monarch Butterfly Biosphere Reserve is a World Heritage Site containing most of the over-wintering sites of the eastern population of the monarch butterfly. (Photo by Carlos Jasso/Reuters)

Dancers rehearse for the Rockettes 2015 Radio City Christmas Spectacular in New York October 15, 2015. (Photo by Lucas Jackson/Reuters)

Central Park Zoo, New York, 1967. (Photo by Garry Winogrand)

People are reflected on a soap bubble lying on a road during the evening in New Delhi, India, June 23, 2015. (Photo by Anindito Mukherjee/Reuters)

Tourists sit around a bonfire on the Makgadikgadi salt pan in Botswana. (Photo by Yang Mengxi/Xinhua News Agency/Barcroft Media)

Revellers take part in New Year's Eve celebrations in Kyiv, Ukraine on December 31, 2020. (Photo by Valentyn Ogirenko/Reuters)

Women stand on a street ahead of the Lunar New Year celebration at the Chinatown in Bangkok, Thailand, February 10, 2021. (Photo by Chalinee Thirasupa/Reuters)