Book excerpt: In the maelstrom of Napoleonic Europe, Britain remained defiant, resisting French imperial ambitions. This Anglo-French rivalry was, essentially, a politico-economic conflict for pre-eminence fought on a global scale and it reached a zenith in 1806-1808 with France's apparent dominance of Continental Europe. Britain reacted swiftly and decisively to implement maritime-based strategies to limit French military and commercial gains in Europe, while protecting British overseas interests. The policy is particularly evident in relations with Britain's 'Ancient Ally': Portugal. That country and, by association her South American empire, became the front line in the battle between Napoleon's ambitions and British maritime security. Shedding new light on British war aims and maritime strategy, this is an essential work for scholars of the Napoleonic Wars and British political, diplomatic, economic and maritime/military history.