This is the history of an idea as much as it is an account of the practice of exerting power. Inasmuch as it bears partly on matters of intellectual history it is really when you think of it, a form of biography “of the means whereby ideas are formed by men, are applied to their daily affairs, and are changed in that process of application”.1 During its most potent years, its adherents, proponents or critics did not call Pax Britannica that. It had no currency in its most formative years. It is a term with retrospective associations. Only late in that epoch did it come to be called that. At the outset of the period, 1815, the practitioners were far too preoccupied with reorganizing an efficient system of global influence and reach to presume that they had come to a state of Pax Britannica. They were, too, mindful of the possible resurgence of those two powers with which they had recently fought major wars: France and the United States. It may be kept in mind that towards the end of Pax, those two powers became complicit or actual allies of Great Britain and the British Empire. They, too, had gone through long changes and accommodations to British power. Throughout most of the years here under consideration, the British contended with the rivalry of these two foreign powers and did so with others of intractable character — Holland in the 1820s in Southeast Asia, Spain in regard to slavery and its nest in Cuba, and Belgium in equatorial Africa in humanitarian matters.