Colorado Gov. John Hickenlooper shows off his socks--one with Democratic presidential candidate Bernie Sanders and the other with Republican candidate Donald Trump – before entering his former brewpub for a book signing event to mark the release of his autobiography Thursday, May 26, 2016, in Denver. Hickenlooper, who is term-limited, is doing book talk rounds this week, reviving speculation that he is positioning himself to join Hillary Clinton's presidential campaign ticket. (Photo by David Zalubowski/AP 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)

American model Emily Ratajkowski and Vanessa Hudgens attend the 73rd Annual Tony Awards at Radio City Music Hall on June 09, 2019 in New York City. (Photo by Mike Coppola/Getty Images for Tony Awards Productions)

A man dressed as Father Christmas learns how to use Zoom on a laptop in the grotto at Bamburgh castle in Northumberland, UK on November 3, 2020, it was due to open on November the 21st but due to the new national lockdown he will now be speaking to the children via Zoom on a computer. (Photo by Owen Humphreys/PA Images via Getty Images)

A woman wearing a face mask to protect against the spread of COVID-19 walks past a mask clad Acrocanthosaurus display at the Witte Museum, Thursday, January 28, 2021, in San Antonio. (Photo by Eric Gay/AP Photo)

A dog catches a wave during the Surf City Surf Dog Contest in Huntington Beach, California September 27, 2015. (Photo by Lucy Nicholson/Reuters)

Pope Francis attends a circus performance during his weekly general audience at Paul VI hall on December 22, 2016 at the Vatican. (Photo by Alberto Pizzoli/AFP Photo)