Why did World War I happen? Several of the oft-cited causes are reviewed and discussed in this analysis. The argument of the alliance systems is inadequate, lacking relevance or compelling force. The argument of an accident or "slide" is also inadequate, given the clear and unambiguous evidence of intentions. The arguments of mass demands focusing on nationalism, militarism, and social Darwinism are also arguably insufficient. They lack indications of frequency, intensity, and process or influence on the various decisions.

1. World wars: definition and causes Richard F. Hamilton and Holger H. Herwig; 2. The European wars: 1815-1913 Richard F. Hamilton; 3. Serbia Richard C. Hall; 4. Austria-Hungary Graydon A. Tunstall, Jr.; 5. Germany Holger H. Herwig; 6. Russia David Alan Rich; 7. France Eugenia C. Kiesling; 8. The United Kingdom J. Paul Harris; 9. Japan Frederick R. Dickinson; 10. The Ottoman empire Ulrich Trumpener; 11. Italy Richard F. Hamilton and Holger H. Herwig; 12. Bulgaria, Romania and Greece Richard C. Hall; 13. The United States John M. Cooper, Jr.; 14. Why did it happen? Holger H. Herwig; 15. On the origins of the catastrophe Richard F. Hamilton; Appendix A. Chronology; Appendix B. Dramatis personae; Appendix C. Suggested readings.