Using an analysis of patterns of international crisis and war from 1948 to 1975, Patrick James suggests why some international crises result in war while others do not. Over 100 cases are used to assess the three most prominent explanations for crisis escalation to war: first, war is the result of rational choice by leaders who expect to gain by it; second, war is the product of the outward projection of political unrest within states; and third, war is the result of a classical balance of power politics. James concludes that the best explanations for war include elements from all three categories. Prior research on war has often lacked rigour. James has tried to remedy this through a long term, comparitive approach to the subject matter.