Robert Denard was a sailor that became a for over 30 years. He fought in Indochina, , Congo, , , Yemen, , , , and the Comoro Islands. At some stage he changed his name to "Gilbert Bourgeaud" and "Saïd Mustapha Mahdjoub," as well as changed his religion from being a Catholic, to Judaism, to , and back to Catholicism. He was married seven times and father to eight children.

He was a resolute anti-communist and fought with the French Navy in Indochina and Algeria. After his service in the Navy he worked as a demonstrator for washing machines in Paris. Unsatisfied, he moved to and worked as a colonial policeman. He began his mercenary career in 1961 in the Congo during the Katanga succession. He fought mostly for ’s African policy but certainly also on his own behalf. It is soundly believed that he had the unspoken backing of both the French state and the French secret service, which tried to maintain French influence over its former colonies. He made headlines after he and his French mercenary group les affreux (the dreadful) rescued civilians that were encircled by rebels in formerly Stanleyville. Denard fought in this region until the secessionist movement collapsed and his men had to flee to Angola. However, Denard returned to the Congo, sympathizing with Katangan separatists and Belgian . Denard was wounded and evacuated with a group of seriously wounded men to former Rhodesia. In January 1968 he invaded the Katanga Province (Congo) in vain on bicycles with a force of one hundred mercenaries, trying to create confusion, which should have enabled a breakout of encircled troops in the town Bukavu.

For ten years he was employed in Gabon by its government. Gabon is located on the equator that made it geographically ideal for military operations on behalf of the French government in Africa. He was also involved in a failed coup attempt in Benin. Ordered by Jacques Foccart, French government chief adviser on African policies, he made four separate attempts to overthrow the government of the small archipelago island nation Comoro. With Denard’s assistance, president took finally the presidency (back) of the . Denard subsequently commanded Abdallah's presidential guard for eleven years. The Comoro islands also served as his base for military operations in and Angola, which made the islands available for France to get around the embargo imposed on South Africa. In 1989, President Abdallah signed a bylaw, ordering the Presidential Guard to be disarmed. However, shortly after the order was given, a military officer allegedly shot Abdallah and wounded Denard. Denard was evacuated via South Africa to France by French paratroopers. Denard faced charges in France with the prosecution stating that Abdallah was shot on orders of Denard. However, he was exonerated due to lack of evidence. In 1995 Denard returned to the Comoros with 33 mercenaries in Zodiac inflatable boats in an attempt a coup against Abdallah’s successor. But the French government sent an expeditionary force GIGN, an elite police tactical unit of the French National Gendarmerie, to capture Denard and his mercenaries. Denard refused to fire at the French special forces unit and surrendered, even though he had well-armed troops and strategically set up heavy machine gun posts. Denard was brought back to France and spent ten months in jail, facing another trial. Denard tried to convince the court that he had acted with the indirect support of French authorities. Nevertheless, Denard was found guilty of "belonging to a gang who conspired to commit a crime." A former head of the foreign intelligence service explicitly stated that in Denard’s defense, "When special services are unable to undertake certain kinds of undercover operation, they use parallel structures. This was the case of Bob Denard."

Denard was sentenced to four years in prison which he never served for he suffered from Alzheimer’s disease by then. He died on 14th October 2007 and his funeral took place in Paris.