wikipedia gives a good time frame.

http://en.wikipedia.org/wiki/World_War_I

international conflict a million: a million)Franc Ferdinand Asassinated with the aid of Serbian Sparking international conflict a million 2)Germany march into Belgium, Britain declare conflict on Germany 3)German’s U-2 submarines sink united statesS Lusitania 4)Zimmerman notes delivered the united statesinto conflict 5)Treaty of Versaille ended international conflict a million international conflict 2: a million)Germany invade Poland sparking international conflict 2 2)Japan attack Pearl Harbor bringing the united statesinto WW2 3)jap Internment camp, All jap in usa have been despatched to camp in the time of the conflict 4)D-Day Allies wreck into Europe 5)Atomic Bomb dropped on Hiroshima and Nagasaki thoroughly destroying the citys.

Wikipidia, look it up, great source of info!