Gustave Bieler was born in Beurlay in France. At the age of twenty, he emigrated to Canada where he settled in the city of Montreal working as a school teacher and then as an official translator for Sun Life Assurance and becoming a Canadian citizen. At the outbreak of World War II, although married with two children, Biéler joined the Canadian Army in Le Regiment de Maisonneuve and was shipped to a base in Britain. His wife Marguerite Geymonat worked as a broadcaster to the troops in Europe on Radio Canada International. Because of his familiarity with France and his fluency in the French and English languages he joined the "Special Operations Executive" in London.
Known by his wartime nickname "Guy," following his specialized training, Colonel Maurice Buckmaster, the SOE commander, wrote in his file that Biéler was the best student SOE had. On November 18, 1942, Biéler, along with wireless operator Arthur Staggs and Michael Trotobas were parachuted into France. Unfortunately, in the dark of the night, Biéler severely injured his back after landing on rocks and he spent several months recovering.
He had strong communication and organizational skills, and as the head of the Musician Network he was able to work with fellow SOE agents and members of the French Resistance to organize very productive sabotage missions. Operating from a base in Saint-Quentin in the northern Aisne département, Biéler's twenty-five teams, scattered over different areas of northern France, were successful in damaging or destroying German gasoline storage tanks, rail lines, bridges, canal locks, and the electric tractors used to tow barges on the shipping waterways. Their repeated efforts hampered the movement of enemy arms and troops but the most important job for Biéler would eventually be the preparations for D-Day.
His operations were so successful that the Germans instituted a special manhunt to get him and his team and on 13 January 1944 the Gestapo arrested him and agent Yolande Beekman in the Café Moulin Brulé in Saint-Quentin. At the Gestapo headquarters there the two were tortured repeatedly but never broke and a few months later Biéler was transferred to Flossenbürg concentration camp in the Oberpfalz region of Bavaria, where the brutal torture continued. Getting nothing out of him, the Germans from whom he gained a great deal of respect, executed a crippled and emaciated Major Guy Biéler by a firing squad with a guard of honour, on 5 September 1944.
Biéler's contribution to freedom was recognized with the Distinguished Service Order (DSO) and he was made a Member of the Order of the British Empire (MBE). In Saint-Quentin, France, he was adopted by the citizens as a folk hero not only for his exploits and bravery but also because he was someone who did everything possible to avoid civilian casualties. The "rue du Commandant Guy Biéler" in Saint-Quentin was named for him 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 département. As well, Major Biéler is recorded on the Groesbeek Memorial in Groesbeek Canadian War Cemetery in the Netherlands. On 22 July 2007 an exhibit on Bieler was unveiled at the opening of the museum in commemoration of all those who suffered and died at the Flossenbürg Camp at Flossenbürg, KZ, Germany. There are memorials honoring Bieler at Morcourt, and Fonsommes (France), on the memorial in a park in Wesmount, (Québec).The Centre Juno Beach at Courseulles-sur-mer has a plaque honoring:"Canadians behind enemy lines. Canadian Agents with the British Special Services". There is a Bieler lake in Canada. The veterans' residence in Montreal (Québec) is named after him.