This book is on the effects of directed energy weapons. That is, how they propagate to and interact with targets. Propagation and target interaction are the key elements in an analysis of a weapon's utility to accomplish a given mission. For example, the effectiveness of a nuclear missile is determined by the yield of its warhead and the accuracy of its guidance, and the effectiveness of a rifle is determined by the type of round fired, the range to the target, and the skill of the soldier who fires it. Directed energy weapons are no different. But while there are books and manuals that deal with the issues affecting the utility of nuclear missiles and rifles, there is no comparable source of information for directed energy weapons. I have tried to fill that void with this book.