This innovative project, to be carried out at Harvard University plus other significant Portuguese collections in Europe, explores the oldest diplomatic alliance in Europe (the ‘Treaty of Windsor’, 1386), which is technically still in force. It explores issues of religious conflict, xenophobia and political propaganda that remain issues in contemporary Europe, providing a historical perspective on European cultural and political integration. Access to American archives and research expertise will bring new methods and materials to this neglected, but significant, alliance. The main output will be a monograph, and an international, interdisciplinary conference in Portugal will develop research networks to publicise research findings to the European academic community.Ratified as an ‘Anglo-Portuguese Alliance’, this pact formed, above all, an alliance against Spain. During the period c.1480-1680 both countries were seafaring empires on the rise, and both saw themselves as having much to fear: from Moorish invasion, from the Jews, but, most especially, from the threat of Spanish domination. The project argues that the rise of the ‘Black Legend’, the systematic demonizing of Spain via the press, was in fact an Anglo-Portuguese alliance. The fear of ‘the other’, of other races and creeds, increased as propaganda about neighbouring countries spread like a virus across the European press.The project will uncover the sources and personnel behind much of this printed literature. It will also uncover the espionage that raged behind the political machines. Newly discovered documents and printed sources in America prove how a Protestant and a Catholic regime united for a common cause: to prevent domination by another country. This will be the first major study to scrutinise their joint actions at home, rather than in the colonies. These complex political manoeuvrings have, for too long, sat in the wings of historical inquiry: this project places them centre stage.