On what date did Britain declare war on Germany following contention over Belgium 's neutrality ?
Germany 's Foreign Minister , Gottlieb von Jagow , said in a speech at the Reichstag that German would respect the guarantees of Belgium 's neutrality , followed by Minister of War Josias von Heeringen , who pledged that " Germany will not lose sight of the fact that the neutrality of Belgium is guaranteed by international treaty . "