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)

This is Raymond, an orphaned koala that was found abandoned beside a road in Brisbane, Australia. He was named after the man who found him.

A man holds onto a tree by the seashore (possibly along the Shore Parkway Greenway) against severe winds during Hurricane Carol's assault on the Northeastern seaboard, Brooklyn, New York, August 31, 1954. (Photo by Hulton Archive/Getty Images)

This photo provided by the Alameda County Sheriff's Office shows a man who was possibly trying to burglarize an abandoned Chinese restaurant in San Lorenzo, Calif., trapped in a grease vent before he was rescued Wednesday, December 12, 2018. Officials say he had been trapped for two days. Deputies and firefighters were called to the vacant building on Wednesday after someone heard cries for help. The sheriff tweeted that the man was trespassing and possibly trying to burglarize the empty restaurant. (Photo by Alameda County Sheriff's Office via AP Photo)

A man is seen wrapped with pythons, some which include the Albino Burmese Python, as part of a show celebrating the coming Year of the Snake in the Chinese calendar, while spectators look on, in Malabon city, north of Manila, Philippines, December 28, 2012. (Photo by Romeo Ranoco/Reuters)

American actor and politician Ronald Reagan stands behind his wife, actor Jane Wyman, who sits down to dinner, circa 1940s. She is seated between two unidentified men, both in military uniforms adorned with Arms Qualification medals, the man on the right with Sharpshooter and Marksman badges and the man on the left, a Captain, with Expert and Sharpshooter badges. Reagan wears a military uniform with Cavalry branch insignia and Wyman wears a black dress with stranded pearl necklace, and a black hat with a veil. (Photo by Hulton Archive/Getty Images)