This book deals with a series of military operations that occurred in Portugal in 1762 and 1763, during the Seven Years' War, and which have been largely dismissed by the historiography. They are collectively called the Guerra Fantastica, 'Fantastical War', given the fact that the military units of the countries involved carried out multiple movements while not engaging in any battle. This work begins with an introduction to the phenomenon of war as a whole, to the environment in Europe at the time, and to the military framework of the conflict. It then describes the events that led to the participation of Portugal in the Seven Years' War and the way in which the conflict in Portugal began. It continues with a presentation of the various forces involved. For this purpose, it analyses in detail the weakness of the Portuguese army, the military reinforcements that were obtained from England, and the arrival in Portugal of the Count of Lippe, whom the King of England had recommended to the King of Portugal to be the commander of the forces, given his recognized ability for the task. It proceeds with an account of the events of the war, starting with an analysis of the invasion of the North of Portugal by the Spanish army and its later withdrawal to Spain. It continues with a description of how the Spanish army, once strengthened by French units, again invaded Portuguese territory, and the events that occurred until its second withdrawal. Despite the numerical superiority of the Bourbon army, the difficulties of the terrain, the efficient command of the Count of Lippe, and the manoeuvres of the Anglo-Portuguese army prevented it from reaching victory and forced its return to Spain. The book is an important piece of research, based on archival material. It explores contemporary correspondence between the Court of Spain and the commanders of the force that invaded Portugal, which is available at the Archive of Simancas. It makes use, moreover, of the correspondence between the Secretary of State of Portugal, the Count of Oeiras, and the Count of Lippe, and between the latter and his subordinate commanders, which is extant at the Military Historical Archive of Lisbon. At the same time, this work is reader-friendly, integrating several notes and original documents that help clarify certain of its major points, as well as a list of the units that participated in the military operations.