OpenStax
Open Stax: World War Ii 1941 1945: Origins of War: Europe, Asia and United States
Examines the conditions that fostered the rise of Fascism and Nazism, the events during the lead-up to the outbreak of war, and what Roosevelt did to help affected nations yet still keep the United States neutral.
Yale University
Tripartite Pact and Associated Documents
This comprehensive site has many documents and essays related to World War II.
Yale University
Yale: Avalon Project: Anti Comintern Pact: German Japanese Agreement
Original document. Contains the German-Japanese agreement and supplementary protocol which was signed at Berlin on November 25, 1936.