The day after sending the ultimatum to Belgium, Germany, continuing the development of the Schlieffen Plan, declared war on France. Both countries were expecting it since they fully mobilized days ago ( two days ago for France ) and by the web of European alliances, were bound to declare war on each other.
Germany’s plan was to avoid a direct confrontation with French forces in the Eastern borders of France and to pass through Belgium then attack the French army behind. However, at the surprise of Kaiser Wilhelm II, by breaking Belgium’s neutrality and independence, Germany finally brought his cousin George V of the United Kingdom into the conflict, on the side of Russia and France.