History of Portugal (1640–1777) put to the test in 1762 when Spain invaded aided by France, during the Seven Years' War. Britain invoked its alliance with Portugal and sent troops. Several months later, the conflict was settled with comparatively little fighting. In 1777, Spain and Portugal signed the Treaty of San Ildefonso, which mainly resolved a number of border disputes between their South American colonies. During the Age of Enlightenment, Portugal was considered one of Europe's unenlightened backwaters; it was a country of three million with 200,000 people in 538 monasteries in 1750. Melo seems to have been deeply embarrassed by Portugal's much lamented
Denmark–Sweden border was still a country although under practical control by Germany). The Nordic Passport Union of 1958 removed passport checks at the border. However, custom checks remained in force between Denmark and other Nordic countries until the Schengen acquis of 2001. There was no land border with Denmark before July 2000 when the Øresund Bridge was opened, which had relaxed customs checks from the start. With the European migrant crisis, Sweden re-introduced stricter border controls in November 2015. Since 4 January 2016, Sweden has required carriers to perform identity checks on the Danish side of the Denmark–Sweden border, while still keeping