The Winding Stair by A.E.W. Mason

In the summer of that same year, the thundercloud burst over Europe, and France, at her moment of need, reaped the fine harvest of her colonial policy. Black men and brown mustered to the call of her bugle as men having their share of France. Gerard de Montignac scrambled like his brother officers to get to the zone of battles. He was seconded in the autumn, was promoted colonel a year later, and was then summoned to Paris.

In a little room upon the first floor in a building adjacent to the War Office Gerard discovered Baumann, of the Affaires Indigènes, but an uplifted Baumann, a Baumann who had grown a little supercilious towards colonels.