Overshadowed by the better known Spanish Armada of 1588, three centuries ago, the final Spanish Armada set sail against England and Scotland. This little known invasion is often treated as part of the little known Jacobite campaign of 1719. However, this invasion and the subsequent campaign in Scotland were part of the virtually unknown War of the Quadruple Alliance. This conflict has never been hitherto covered in a book in the English language. This book is a study of war and diplomacy involving several of the European powers, with fighting on the high seas, in Scotland, Spain, Sardinia, and Sicily. It is a tale of a once great power taking advantage of apparently favourable international circumstances to regain parts of its lost empire. Success seemed possible, but the fortunes of war are fluctuating and luck only goes so far. Eventually the realities of military power reasserted themselves with bloody results. This book presents an account of this little known war. The emphasis is on Britain’s naval, diplomatic and military efforts, whilst not neglecting those of its allies and enemies, both abroad and at home. It draws on a variety of little or unused primary sources held at the National Archives and elsewhere and boasts a cast of interesting and unusual characters.