The French plan to respond to a German offensive was a counteroffensive into the German center. The French attempted this on August 21-23; it was an utter failure.
The outbreak of the Great War saw one of the German Navy's newest and most powerful battlecruisers in the Mediterranean. She was a threat to the Entente and had to be stopped. Only...what exactly is she trying to do?
The German war plan called for a massive offensive against France that would pass through Belgium, but one of the big unknowns in German war planning was whether the Belgians would resist, and if so, how fiercely.
French strategists emphasized the importance of offense and planned to respond to a German invasion with an offensive of their own. British strategy increasingly revolved around joining with France in a ground war.