At the end of a grueling day, Mr. Liebling related, “a G-2 (intelligence) officer came out of the staff tent” to talk to the Britons. “He had a bottle of whiskey with him, which was an excellent idea, because they were pretty well done in by that time. After half an hour, he climbed out and told us that he thought they were all right.”

Willis Michael Sadler — known to friends as Mike — was born in London on Feb. 22, 1919, to Adam and Wilma Sadler and was raised in Stroud, a village in Gloucestershire about 110 miles to the west. His father was the manager of a plastics factory. Mike attended the Oakley Hall School in Cirencester and the Bedales School in Hampshire. After graduation in 1937, he moved to Southern Rhodesia, his imagination fired by boyhood tales of adventure in a land of lions and elephants. With family connections, he got a job on a tobacco farm, where he worked until the war broke out.

After his North Africa adventures as a desert navigator, Mr. Sadler returned to England and in 1944 parachuted into France after the Allied invasion of Normandy. He participated in sabotage operations against German occupation forces and won the Military Cross for bravery in action behind enemy lines.

He and his wife, Patricia, whom he married after the war, had a daughter, Sally Sadler, who survives him. His wife is deceased. Until he moved to his Cambridge nursing home a couple of years ago, he lived in Cheltenham, Gloucestershire, 90 miles west of London.

After the war, he went on a one-year expedition to Antarctica with an S.A.S. colleague, Maj. Blair (Paddy) Mayne, who was Colonel Stirling’s successor in the S.A.S. Mr. Sadler later joined the British Foreign Office for what may have been classified work. Friends and journalists who interviewed him said he steadfastly declined to discuss his postwar activities beyond saying it was “foreign service work.”

Mr. Sadler had gradually lost his eyesight, but he marked his 100th birthday in 2020 with a celebratory gathering of friends at the Special Forces Club in London. “He spoke to me enthusiastically about it on the phone,” his friend Dominique Legrand said, “and his voice was as energetic as ever.”

Alex Traub contributed reporting.

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