Is this a private fight or can anybody join?

"Is This a Private Fight explores why some countries join interstate wars well after the war has begun, waiting months and often years before joining wars and thus changing their beliefs about the wisdom of entering a war. It argues that unexpected or 'surprising' events in wars cause neutral players to update their expectations about the trajectory of the war, leading them, at times, to change their status and join. This explains why some wars spread while others do not. Shirkey uses a combination of case studies and statistical analysis to test this theory: the Crimean War, the Franco-Prussian War, World War One, and a case on the spread of war since World War Two. Designed for upper level undergraduate and graduate classes focused on war and other international security issues, this book is a must read."--Book cover.