France–Germany border

A French Rhine

Alsace and Lorraine were at the centre of Charlemagne’s empire and later part of the German lands of the Holy Roman Empire. The Peace of Westphalia of 1648 gave control of them to France.^[2] Next door, France also held the Saar from 1684 to 1697 and again from 1792 to 1815. After Napoleon’s defeat it had to give most of the Saar to Prussia.^[3]

Between Basel and the mouth of the Lauter the Rhine itself forms the border, with France on the west bank and Germany on the east.^[1]

1871: Alsace-Lorraine

In the Franco-German War of 1870–71 a coalition of German states led by Prussia defeated France, and Germany was unified.^[4] The Treaty of Frankfurt, signed on 10 May 1871, ended the war.^[4] France ceded 13,123 km² of Alsace and Lorraine, taken in part because of its large German-speaking population, and lost valuable iron ore and steelworks with it.^[2]

The new Reichsland (imperial territory) was denied real self-government until 1902. Thousands of residents who saw themselves as French emigrated, and the loss fed a desire for revenge in France that helped lead to the First World War.^[2][4]

Back and forth

After Germany’s defeat in the First World War, Alsace-Lorraine was returned to France in 1919. Germany took it again in 1940, and it went back to France in 1945.^[2]

After 1919 the Saar, north of Lorraine, was run by the League of Nations for 15 years, and its coal mines were given to France. In a plebiscite on 13 January 1935 more than 90% of its voters chose Germany.^[3] France occupied it again in 1945. In a referendum on a 1954 plan for a European-supervised autonomous Saar, 68% of its voters said no; France agreed in 1956 to its return, and on 1 January 1957 it became a state of West Germany.^[3]

Taking the checks away

On 14 June 1985 France, West Germany, Belgium, Luxembourg and the Netherlands signed the Schengen Agreement at Schengen, in Luxembourg, agreeing to reduce checks at their shared borders. It took effect in March 1995.^[5]