It has been said that the taking of a fortress depends primarily on the making of a good plan to take it, and the proper implementation and application of the resources to make the plan work. Long before a fortress has been besieged and conquered, it has to have been out-thought before it can be outfought. A siege can be described as an assault on an opposing force attempting to defend itself from behind a position of some strength. Whenever the pendulum of technology swings against the "status quo," the defenders of a fortification have usually been compelled to surrender. This book contains examples of sieges, both successful and unsuccessful, demonstrating that no matter how securely a fortress or defensive position is constructed and defended, eventually a good plan and a determined besieger can overcome it. One way or another, time, willpower and determined effort will be brought together in sufficient quantity and quality to bring a siege or a defense to a successful conclusion. It will be argued through the examples presented in this book that ultimately, "no fortress is impregnable."