He was governor of Niger, Dahomey, French Somaliland and Guinea.
There he was particularly involved in recruiting African soldiers during the First World War.
Similar to Félix Éboué, who also had a black skin color and was not born in Africa, the French colonial administration calculated so that Blacher could take on the role of a "middleman" between the African people and their European rulers.
He was appointed governor of the Nigerian colony of French West Africa in 1930, which he remained until 1931.
In October 1938, married Blacher in Conakry, the artist Béatrice Appia, widow of Eugène Dabit.