Ben Bella had to communicate with his fellow Arab nationalists in French since his own Arabic was poor.

From Small Wars, Faraway Places by Michael Burleigh. Page 321.

The Second World War had raised the national consciousness of many of the Algerians who fought for France, while the collapse of France in 1940 had lowered its prestige in the eyes of Arabs, who were treated like dirt by French settlers. Chronic food shortages added to the tensions. The first covert armed Algerian nationalist movement was established in 1947 as the Organisation Spéciale, but this had been crushed by 1951. Its ranks included Ben Bella, who after the war had declined a regular army commission to become a local government councillor in Marnia, where his family had a farm. In 1947 he was subject to obscure chicanery about ownership of his farm, which like all Arab land lacked title deeds. He fled after shooting one of his would-be dispossessors. In 1949 he planned a robbery on the Oran Post Office to garner funds for the underground ‘army’ which was not even a band. Careful police work led to his arrest and imprisonment. In 1953 Ben Bella broke out of jail with the aid of a file hidden in a baguette, fleeing to Cairo, where he had to communicate with his fellow Arab nationalists in French since his own Arabic was poor.