The nineteenth century started under the shadow of Napoleon, whose ambitions and course of life nobody could have foreseen at the time but, because of which, practically all European countries were to suffer long years of a ruthless war. Portugal, a small country with no political strength, had however a strategic relevance in the maritime trade between north Europe and the rest of the world. This was very important as far as England was concerned, because accessing Britain's naval and commercial might was Napoleon's most desired and ultimate goal. Between Portugal and the United Kingdom there was an alliance of mutual support in peace and war, still the oldest in the world, and the fulfilment of the implied duties was the real reason that made the Portuguese sea coast and politics particularly interesting for the emperor's projects.

The close connection between Portuguese, English and French ideologies during the four years the armies of the three countries coexisted in Portugal was perhaps the most direct cause of the spread of Liberal ideas that would change political and social life in Portugal, with the negative result of serious unrest, persecutions and a civil war that lasted for almost the entire first half of the nineteenth century.

The course of this period in Portugal is so entangled and difficult to follow, with the undecided diplomatic and actual positions taken by other countries, whose support was absolutely necessary to strengthen the small and unprepared Portuguese troops, that the general public has no clear idea about what really happened in Portugal at that time. Consequently, the development of the history of Portugal in the second half of the nineteenth century, both within Europe and overseas, particularly in Africa and Asia, deeply changed in a way never to return to the old order. That is why a detailed work like the one now presented is a fundamental contribution to the knowledge and understanding of what the nineteenth century really meant: the most agitated, devastating and bloody period in Portuguese history, changing the nation's course quickly and deeply. The same can be said about Spain, the Iberian country that Lord Holland preferred and whose history at that time ran parallel to that of Portugal.