Models prepare backstage before a presentation as part of Fashion Weekend Plus Size Summer 2015 collection show in Sao Paulo, July 25, 2015. (Photo by Nacho Doce/Reuters)

A motorcyclist dodges in the annual water-splashing festival to mark the New Year of the Dai minority in Menglian, Yunnan province April 13, 2015. (Photo by Wong Campion/Reuters)

“Sokolica”. Sokolica, Poland. (Photo and caption by Marcin Kęsek/National Geographic Traveler Photo Contest)

ATTENTION! All pictures are presented in high resolution. To see Hi-Res images – just TWICE click on any picture. In other words, click small picture – opens the BIG picture. Click BIG picture – opens VERY BIG picture.

Tong Jieping, 44-year-old mentally disabled patient, is chained by his foot inside his room, in Qunxing village of Wangjiang county, Anhui province, China, July 14, 2015. Tong was diagnosed mentally ill when he was in his 20s. His parents, both in their 70s, could not afford the medical treatments so they had to lock him up in chains to prevent him from running away, according to Tong's family. (Photo by Reuters/Stringer)

Actress Penelope Cruz attends a photocall promoting the film “Chromophobia” at the Palais during the 58th International Cannes Film Festival May 21, 2005 in Cannes, France. (Photo by M. J. Kim/Getty Images)

Participants take part in the annual Great Spitalfields Pancake Race in aid of London's Air Ambulance in London, Britain February 9, 2016. (Photo by Stefan Wermuth/Reuters)

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)

Metropolitan Transit Authority (MTA) Police Officer Keith Flood trains with his K-9 partner Doc, a German Shepherd, inside the “warehouse room” at the new MTA Police Department Canine Training Center in Stormville, New York, U.S., June 6, 2016. (Photo by Mike Segar/Reuters)