Complex sentence: A final assault battle of the Marne and in Champagne developed into a defensive battle between Soissons and Reims, and between Marne and Vesle, at the end of the German troops were driven back to a line before the spring offensive.
Split into simpler sentences: A final assault battle of the Marne and in Champagne developed into a defensive battle, between Soissons and Reims, and between Marne and Vesle. In the end the German troops were driven back to a line before the Spring Offensive.