He is the founder of the Yahad-In Unum, an organization dedicated to locating the sites of mass graves of Jewish victims of the Nazi mobile-killing units in the former Soviet Union.
From 1992-99, he served as Secretary of Jewish Relations for Cardinals Albert Decourtray, Jean Balland and Louis-Marie Billé.
Its largest and most ambitious initiative is to locate the sites of mass graves of Jewish victims of the Nazi mobile killing units, the Einsatzgruppen, in the former Soviet republics and Eastern bloc.
[6] Between 2015 and 2016, he taught at the Program for Jewish Civilization in the Edmund A. Walsh School of Foreign Service, Georgetown University as an adjunct professor.
[7] Since 2016 he is the inaugural holder of the Braman Endowed Professorship of the Practice of the Forensic Study of the Holocaust at the Center for Jewish Civilization at Georgetown University.
[8] Father Desbois' interest in the Holocaust started at a young age, because his grandfather, who helped raise him, was a French soldier who had been deported to the Nazi prison camp in Rava-Ruska during World War II.
As a consequence of his childhood interests, Father Desbois studied the Jewish faith while preparing for his ordination as a Catholic priest.
[1] Upon his arrival, he was shocked to discover that there existed not a single marking or commemoration to 1.25 million Jewish victims in all of Ukraine and Belarus.
Speaking of his initial experience, Desbois narrated how:In 2002, while traveling in Ukraine, he visited the site of his grandfather's imprisonment, Rawa-Ruska.
The organization collects information about the mass killing of Jews and Roma in Ukraine, Russia, Belarus, Lithuania, Poland, Moldova and Romania between 1941 and 1944.
Using metal detectors, Desbois and his team have unearthed German cartridges and bullets from the pits where bodies were thrown, as well as jewelry belonging to the victims.
[10] Paul Shapiro of the United States Holocaust Memorial Museum has countered that: "Some people have been critical of his methodology, but no one else is going out and doing this kind of work.
In July 2017, Pope Francis sent a blessing and a message of encouragement to Father Desbois and Yahad-In Unum, writing:[12] The Holy Father encourages the members of ‘Yahad-In Unum’ to continue their struggle for the just recognition of the violence suffered by so many men and women belonging to different communities.
[17] Due to his position as Director of the French Episcopal Conference's Committee for Relations with Judaism, Father Desbois has had to deal with the controversy following negationist comments made by SSPX bishop Richard Williamson.