The Armada was a great Spanish fleet assembled in 1588 as part of the attempt by Philip II to invade England.  Philip had come to believe that only conquest could halt English aid to the rebels against Spain in the Low Countries or stop the English depredations in the New World. The plan was to send a fleet of 130 ships commanded by the duque de Medina Sidonia (1550-1619) to cover an invasion force from Flanders under Alessandro Farnese. This plan proved strategically unsound and beyond Spain's logistical capabilities.

When the outgunned and inadequately provisioned Armada appeared off Plymouth on July 30, it was met by an English fleet of equal or superior strength. In spite of the efforts of Francis Drake, Martin Frobisher, John Hawkins, and other English captains (Sea Dogs), the Spanish maintained their order of battle and lost only two ships before arriving at Calais. The rendezvous with Farnese failed, however. Lacking adequate ships of his own and blockaded by Dutch rebels whose shallow-draft flyboats easily eluded the Spanish galleons, Farnese could not embark his troops. Then, on August 8, English fire ships drove the Armada out of its Calais anchorage. The Spanish regrouped and fought another action off Gravelines, but they were now out of ammunition. Realizing that the situation was lost, Medina Sidonia sailed north around Scotland and Ireland and returned to Spain. He suffered heavy losses because of disease and shipwreck.

The defeat of the Armada did not affect the naval balance of power: England had been a major sea power before 1588, and the Spanish fleet was quickly rebuilt afterward. It did demonstrate that Spain lacked the power to impose religious unity on Europe.