"Before and during the World War, all the different races serving in the French Army were excellently officered by subalterns and non-coms born in North Africa, but of European ancestry: by sons of immigrated colonists of French, Spanish and Italian extraction.
"The late Marshal Lyautey used to say of these sons of European settlers: 'Their knowledge of the ways of the natives is priceless, because they have assimilated it from childhood. In the native regiments, they constitute a human concrete, which keeps together men of antagonistic races and beliefs'"
From Amazon:
Colonial Conscripts: The Tirailleurs Senegalais in French West Africa, 1857-1960