2.  1914-1918  Central Powers (Germany and Austria- Hungry) vs. Allied Powers (France, United Kingdom, and Russia)  Austria’s Archduke Franz Ferdinand and his wife Sophie were assassinated by a Serbian nationalist

3. May 7, 1915: Sinking of the British passenger liner RMS Lusitania by German U-Boat (submarine) January 1917: Zimmerman Telegram

4. British ocean liner 159 American passengers onboard; 128 Americans killed Traveling from New York to Liverpool German U-boat (U-20) fired a torpedo on May 7 at 1:40pm

5. German Foreign Minister Arthur Zimmermann to German Ambassador in Mexico Heinrich von Eckhardt Start unrestricted submarine warfare Promised portions of the United States in return for Mexico joining World War I against United States British intercepted, translated, and shown to the United States

6. We intend to begin on the first of February unrestricted submarine warfare. We shall endeavor in spite of this to keep the United States of America neutral. In the event of this not succeeding, we make Mexico a proposal of alliance on the following basis: make war together, make peace together, generous financial support and an understanding on our part that Mexico is to reconquer the lost territory in Texas, New Mexico, and Arizona. The settlement in detail is left to you. You will inform the President of the above most secretly as soon as the outbreak of war with the United States of America is certain and add the suggestion that he should, on his own initiative, invite Japan to immediate adherence and at the same time mediate between Japan and ourselves. Please call the President's attention to the fact that the ruthless employment of our submarines now offers the prospect of compelling England in a few months to make peace. Zimmermann

7. April 6, 1917: United States declares on Germany May 18, 1917: Selective Service Act (Selective Draft Act) Allowed Federal Government to raise national army for entry into World War I All males between 21 to 31 were required to register for military service

8. As sung by early-20th century recording artist Billy Murray:Billy Murray Verse 1 Johnny [2], get your gun, get your gun, get your gun. Take it on the run, on the run, on the run. Hear them calling you and me, Every Son of Liberty. Hurry right away, no delay, go today. Make your Daddy glad to have had such a lad. Tell your sweetheart not to pine, To be proud her boy's in line. [2]Son of Liberty Verse 2 Johnny, get your gun, get your gun, get your gun, Johnny, show the "Hun" [3] you're a son- of-a-gun. Hoist the flag and let her fly. Yankee Doodle [4] do or die. Pack your little kit, show your grit, do your bit. Yankee [5] to the ranks from the towns and the tanks. [6] Make your Mother proud of you And the old red-white-and-blue [7]Hun [3]Yankee Doodle [4]kit [5] [6]red-white-and-blue [7] Chorus Over there, over there, Send the word, send the word over there That the Yanks are coming, the Yanks are coming The drums rum-tumming everywhere. So prepare, say a prayer, Send the word, send the word to beware - We'll be over, we're coming over, And we won't come back till it's over, over there.Yanks