Peninsular War: French troops engage British-Portuguese forces in the Battle of Majadahonda.

The Peninsular War (1808–1814) was fought in the Iberian Peninsula by Portugal, Spain and the United Kingdom against the invading and occupying forces of the First French Empire during the Napoleonic Wars. In Spain, it is considered to overlap with the Spanish War of Independence.

The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Northwestern Europe, off the coast of the continental mainland. It comprises England, Scotland, Wales and Northern Ireland. The UK includes the island of Great Britain, the north-eastern part of the island of Ireland, and most of the smaller islands within the British Isles, covering 94,354 square miles (244,376 km²). Northern Ireland shares a land border with the Republic of Ireland; otherwise, the UK is surrounded by the Atlantic Ocean, the North Sea, the English Channel, the Celtic Sea and the Irish Sea. It maintains sovereignty over the British Overseas Territories, which are located across various oceans and seas globally. The UK had an estimated population of over 68.2 million people in 2023. The capital and largest city of both England and the UK is London. The cities of Edinburgh, Cardiff and Belfast are the national capitals of Scotland, Wales and Northern Ireland respectively.

Portugal, officially the Portuguese Republic, is a country on the Iberian Peninsula in Southwestern Europe. Featuring the westernmost point in continental Europe, Portugal borders Spain to its north and east, with which it shares the longest uninterrupted border in the European Union; to the south and the west is the North Atlantic Ocean; and to the west and southwest lie the Macaronesian archipelagos of the Azores and Madeira, which are the two autonomous regions of Portugal. Lisbon is the capital and largest city, followed by Porto, which is the only other metropolitan area.