After exercises and diplomatic visits, Britain and France divided Atlantic trade protection responsibilities, assigning the central Atlantic to France. Dunkerque operated from Brest with Bearn, while Strasbourg worked from Dakar with HMS Hermes. Hermes had been conceived as a reconnaissance carrier able to find targets for fast capital ships, so her aircraft complemented Strasbourg's speed and gun power in raider hunting. Dunkerque later backed Hood in the unsuccessful hunt for Scharnhorst and Gneisenau, a matchup close to the threat the French ships had been designed to defeat and one the German ships could not easily evade.
Chapter · 48:47-52:57
Anglo-French planning assigned the Dunkerques to raider hunting
The sisters became the First Battle Division and then covered the central Atlantic, splitting between Brest and Dakar to hunt German commerce raiders.