Anglo-Portuguese Treaty of 1373

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Anglo-Portuguese Treaty of 1373" – news · newspapers · books · scholar · JSTOR (December 2020) (Learn how and when to remove this message)

The Anglo-Portuguese Treaty of 1373 was signed on 16 June 1373^[1] between King Edward III of England and King Ferdinand I and Queen Leonor of Portugal. It established a treaty of "perpetual friendships, unions [and] alliances" between the two seafaring states.^[2][3][4] It is the second oldest continuous treaty in effect to this day, signed just a few years after the Auld Alliance.^[5][6]

It was reinforced throughout history, including in 1386, 1643, 1654, 1660, 1661, 1703, 1815, and by a secret declaration in 1899. It was recognised in the Treaties of Arbitration in the 20th century between Britain and Portugal in 1904 and 1914.^[7]

The treaty was temporarily void during the Iberian Union from 1580 to 1640, when the monarchies of Spain and Portugal were in a dynastic union.^{[citation needed]} However, with Portugal's restoration of independence, the alliance returned and came to a new height during the Napoleonic Wars when the British sent their best general, the Duke of Wellington, to sap Napoleon's armies in the Peninsular War.^{[citation needed]}

It was activated again during the Second World War, whereupon the Portuguese remained neutral, in agreement with Britain,^[7] which did not want to bring the war into the Iberian Peninsula. This lasted until 1943, when, after three months' negotiations, it was fully reactivated by the National Government of Winston Churchill and Portugal.^[7] Britain was accorded aerodrome and nautical facilities in the Portuguese Azores to help combat the U-boat threat. The British also cited the treaty during the 1982 Falklands War.^{[citation needed]}

The 650th anniversary of the treaty was officially commemorated by the governments of both nations on 16 June 2023, and in acknowledgement that this represents "the world's longest diplomatic alliance".^[8]