Our interest in the subject of blockades came about when we were both asked to discuss the work of David Surdam on the American Civil War blockade imposed by the Northern states on the Confederacy. Surdam's analysis of this case was thorough and his general conclusions were quite interesting. What we became curious about was whether other of the notable blockades of the past two centuries had similar outcomes, and if not, why not. As we began to examine other blockades, we found that there was a considerable body of international law that had some influence on the outcomes but whose changes over time reflected changing political, economic, and military factors. The blockades of interest were not just those for military purposes in wartime but also Pacific blockades, or sanctions, presumably imposed in the attempt to prevent warfare.

The study of blockades posed many interesting economic issues and there were available considerable amounts of quantitative data to permit much statistical analysis. This aspect of the study fits well with our professional background. There were two possible problems that we do not believe seriously weaken the analyses in the book. First, we had no formal training as military historians, nor did we seek to utilize naval archives to obtain primary material. Nevertheless, there have been ample amounts of material collected in secondary sources, and there is an extremely rich body of important work by military historians for us to utilize for quantitative and qualitative information.