Nationalism militarism allies central powers balance of power archduke franz ferdinand trench warfare "no man's land" lusitania sussex pledge zimmermann note selective service act convoy system american expeditionary force (aef) john j. pershing conscientious objector armistice war industries board (wib) bernard m. baruch propaganda committee on public information george creel espionage and sedition acts great migration fourteen points self-determination league of nations treaty of versailles reparations war-guilt clause