what were the key events of ww1?
['June 28, 1914. Archduke Francis Ferdinand is assassinated.', 'July 28, 1914. Austria-Hungary declares war on Serbia, beginning World War I.', 'August 2-7, 1914. Germany invades Luxembourg and Belgium. ... ', 'August 10, 1914. Austria-Hungary invades Russia.', 'September 9, 1914. ... ', 'February 18, 1915. ... ', 'April 25, 1915. ... ', 'May 7, 1915.']