World War I:
War is Declared!
July 21, 1914: Austria-Hungary and its ally Germany declare war on Serbia.
August 1, 1914: Germany declares war on Serbia's ally Russia.
August 3, 1914: Germany declares war on Russia's ally France.
August 1914: Germany invades Belgium, violating an 1839 treaty where Belgium is to remain neutral territory.
August 1914: Great Britain agrees to protect Belgium