Possible Clues:

• "Over There" conflict, briefly
• It ended at 11:00 on 11/11
• La Belle Époque ender: Abbr.
• 20th-cen. global conflict
• Big conflict of the 1910s, briefly
• The 1919 Treaty of Versailles concluded it: Abbr.
• Event from 1914-1918
• It began 7/28/1914
• It marked the beginning of the "Lost Generation"
• The Ottoman Emp. fell shortly after it