Treaty of Windsor, 1386

Treaty of Windsor

England and Portugal concluded a pact of perpetual friendship and mutual support — the basis of the Anglo-Portuguese alliance, the oldest alliance in the world still in force.

Date

9 May 1386exact dateDate in the Julian calendar

Place

Windsortoday: Windsor, Berkshire, United Kingdom · Western and Central Europe

Participants

Kingdom of Portugal, Kingdom of England, John I of Portugal

Threads

History of Portugal since the Battle of Aljubarrota

Also known as

Anglo-Portuguese Alliance; Англо-португальский союз

The treaty confirmed the agreement of 1373 and the cooperation that had helped John I win at Aljubarrota. The alliance was sealed in February 1387 by the marriage of John I to Philippa of Lancaster, daughter of John of Gaunt; their sons — the future King Edward (Duarte), Peter and Henry the Navigator — led Portugal into the age of overseas expansion.

Over the following centuries the alliance was invoked many times: in the war of independence against Spain after 1640, in 1807, when the British fleet escorted the Portuguese court to Brazil, and in 1943, when Portugal let Britain use bases in the Azores. Its gravest crisis was the British Ultimatum of 1890.

The treaty is usually dated 9 May 1386; some accounts give February 1387, the month of the royal wedding.

Connections

Causes and preconditions

Battle of Aljubarrota14 August 1385 · Western and Central Europethe victory, won with the help of English archers, was followed by a permanent alliance with England

Related events

Transfer of the Portuguese court to Brazil29 November 1807 – 8 March 1808 · Latin Americain 1807 the navy of Portugal’s oldest ally escorted the royal family to Brazil

British Ultimatum of 189011 January 1890 · Western and Central Europethe ultimatum of 1890 was the gravest crisis of the alliance

Same participants

Same place

End of Roman rule in Britain383–410 · Western and Central Europe

Magna Carta15 June 1215 · Western and Central Europe

Slave Trade Act 180725 March 1807 · Western and Central Europe