Complex sentence: In 1630 Turenne left the Netherlands and entered the service of France, motivated not only by the prospect of military advancement but also by his mother's desire to show the loyalty of the Bouillon dominions to the French crown.
Split into simpler sentences: In 1630 Turenne left the Netherlands and entered the service of France. This step was dictated not only by the prospect of military advancement but also by his mother's desire to show the loyalty of the Bouillon dominions to the French crown.