John Macalister graduated from the University of Toronto, then as a Rhodes Scholar studied at Oxford University. He was expanding his education further at the Institute of Corporate Law in Paris, France when World War II began in 1939. Macalister tried to join the infantry but his eyesight was such that he needed thick glasses and as such could not be placed on active duty. However, fluent in the French language, John Macalister volunteered for the Special Operations Executive F Section where as an agent in France, his thick glasses would actually add to his disguise.
Together with fellow Canadian, Frank Pickersgill, John Macalister was parachuted into occupied France on June 20, 1943 to work as wireless operator for the "Archdeacon" network in the Ardennes area. They were met by agent Yvonne Rudelatt, but were stopped by the Gestapo who had been tipped by an informer. Although they tried to get away, shots were fired and Rudelatt was hit causing the car to crash. They were taken to Fresnes prison where they were interrogated and tortured repeatedly. Macalister steadfastly refused to reveal his security checks to the Germans who had his codes and were anxious to send misleading messages back to the SOE's London headquarters. Macalister gave his interrogators nothing and when his captors tried to send messages, SOE recognized them as fake.
Unable to get anything of value from him, John Macalister, along with Frank Pickersgill and Roméo Sabourin, were shipped to Buchenwald concentration camp on August 27, 1944. They were known as the Robert Benoist group executed at Buchenwald concentration camp on September 14, 1944.
Captain John Macalister is honored on the Brookwood Memorial in Brookwood, Surrey, England and as one of the SOE agents who died for the liberation of France, he is listed on the "Roll of Honor" on the Valençay SOE Memorial in the town of Valençay, in the Indre departément of France.