A three-month-old Sumatran tiger cub named “Bandar” shows his displeasure after being dunked in the tiger exhibit moat for a swim reliability test at the National Zoo in Washington, on November 6, 2013. All cubs born at the zoo must take a swim test before being allowed to roam in the exhibit. Bandar passed his test. (Photo by Manuel Balce Ceneta/Associated Press)

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)

Marines of the Baltic Fleet forces of the Russian Navy train in the zone of obstacles during military exercises at the Khmelevka firing ground in the Kaliningrad region, Russia on November 24, 2021. (Photo by Vitaly Nevar/Reuters)

Police officers introduce a litter of golden retriever puppies to be trained as police dogs during a ceremony at the National Police Academy in La Paz, Bolivia, Monday, August 16, 2021, the date of the feast day for Saint Roch, considered the patron saint of dogs, among other things. (Photo by Juan Karita/AP Photo)

Mahsa Kadkhoda #11 of Team Iran spikes the ball during their semi-final round match against Team Chinese Taipei on day seven of the AVC Cup For Women at PhilSports Arena on August 28, 2022 in Pasig, Philippines. (Photo by Ezra Acayan/Getty Images)

A grey squirrel looks for some food from a girl in the Botanic Gardens in Glasnevin, Dublin, Ireland on April 3, 2023. (Photo by Damien Eagers/The Irish Times)

A South American Coati licks a block of frozen fruits at Israel's Safari Zoo in Ramat Gan, north of the Mediterranean coastal city of Tel Aviv, as temperatures reach 35 degrees Celsius on July 13, 2023. (Photo by Jack Guez/AFP Photo)

Sir Argus, centre, with Brian Hayes up, jumps the first during the Guinness Beginners Steeplechase, alongside eventual winner Mars Harper, right, with Sam Ewing up, during day four of the Galway Races Summer Festival at Ballybrit Racecourse in Galway, Ireland on August 3, 2023. (Photo by Seb Daly/Sportsfile)