World War I

5. Clause in the Treaty of Versailles that assigned responsibility for the war to Germany
6. Poisonous gas used for the first time in this war
8. Weapon that could fire rapidly and played a significant role in the war
9. British passenger liner sunk by a German U-boat in 1915
12. Conflict in which entire societies and economies are mobilized
14. Large German airship used for bombing raids
15. Treaty that ended World War I and imposed harsh penalties on Germany

1. Assassinated Archduke Franz Ferdinand, sparking the war
2. German submarines used to sink Allied ships
3. Style of fighting that characterized the Western Front
4. Area between opposing trenches
7. Ceasefire that ended the fighting on November 11, 1918
10. Partnerships between countries that contributed to the outbreak of war
11. Site of a brutal battle in 1916 that resulted in over one million casualties
13. US president during WWI and a key player in the Treaty of Versailles negotiations