[1][2] In early 1962, he denounced the urban warfare that occurred during the Algerian War as "an offense against God,"[3] to the anger of the pieds-noirs of his flock, who subsequently called him "Mohammed Duval."

Duval, assisted by Cardinals Julius Döpfner and Raúl Silva Henríquez, delivered one of the closing messages of the Council on 8 December 1965.

He occupied Room 86 at the cardinal electors' residence for the August 1978 conclave, sharing a shower with Leo Suenens, Raúl Silva Henríquez, and Juan Ricketts.

[6] Because of his humanitarian and anti-imperialist works, the Duval was chosen by the Revolutionary Council as one of four clergymen who would visit the hostages held in the American embassy in Tehran on Christmas Day 1979.

Following his death, John Paul II remarked that, "He will remain a light and an encouragement on a long and difficult road at a moment in which the Christian community in Algeria is facing testing times".