The Berlin Wall: Map of Divided Berlin and Germany

After Nazi Germany surrendered on 8 May 1945, the victorious Allies split the country into four occupation zones: American in the south, British in the north-west, French in the south-west and Soviet in the east. Berlin lay about 160 km inside the Soviet zone, but as the capital it was divided into four sectors in the same way. Germany's lands east of the Oder and Neisse rivers were placed under Poland and the Soviet Union.

The four powers were supposed to run Germany together, but the Cold War broke their alliance apart. They disagreed over reparations, over the Marshall Plan and over what kind of state Germany should become. When the western zones introduced a new currency, the Deutsche Mark, in June 1948, the Soviet Union blockaded the land routes to West Berlin. For almost a year the Western Allies flew in food and coal, about 2.3 million tonnes in more than 270,000 flights, until the blockade was lifted on 12 May 1949.

Within months there were two German states. The Federal Republic of Germany (West Germany) was founded in the three western zones on 23 May 1949, with Bonn as its capital. The German Democratic Republic (East Germany) followed in the Soviet zone on 7 October 1949, with East Berlin as its capital. Use the 1945 and 1949 buttons above the map to compare the zones with the two states.

From 1952 East Germany closed and fortified its long border with West Germany, but inside Berlin people could still cross between the sectors by underground, train or on foot. Berlin became the loophole through which East Germans left. Between 1949 and 1961 about 2.7 million people fled, many of them young doctors, engineers and skilled workers whom the planned economy could not afford to lose. In July 1961 alone more than 30,000 people left.

In 1958 Soviet leader Nikita Khrushchev demanded that the Western Allies leave West Berlin. They refused, and in summer 1961 East German leader Walter Ulbricht won Moscow's approval to close the sector border. On 15 June he had told journalists that "no one has the intention of building a wall". Eight weeks later, in the early hours of Sunday 13 August 1961, police and soldiers rolled out barbed wire along the boundary of West Berlin, tore up streets and cut railway lines. Concrete blocks followed from 15 August.

The Wall did not run between East and West Germany but completely surrounded West Berlin, which became an island 160 km inside East German territory. About 43 km of it divided the city itself, along the old boundary between the Soviet sector and the American, British and French sectors, past the Brandenburg Gate, along Bernauer Straße and through the river Spree. The other 112 km or so separated West Berlin from the surrounding East German countryside of Brandenburg.

The line on the map follows the Berliner Mauerweg, the 160 km trail laid along the former Wall. The barrier stood a few metres inside East German territory, and behind it lay a "death strip" of raked sand, floodlights, patrol roads, dog runs, signal fences and watchtowers, with a second wall on the eastern side. Over the years the Wall was rebuilt four times; the final version, from 1975, was made of L-shaped concrete segments about 3.6 m high with a pipe along the top to stop climbers.

Crossing points for foreigners, West Germans and West Berliners included Checkpoint Charlie on Friedrichstraße, the Bornholmer Straße bridge, the Invalidenstraße crossing, Friedrichstraße station and Dreilinden on the autobahn to West Germany. East Germans could not cross at all without special permission.

The Wall split streets, families and friends overnight. People escaped by jumping from windows on Bernauer Straße, through tunnels, in hidden car compartments, across the Spree and even by hot-air balloon. About 5,000 people managed to escape over or under the Wall. Research by the Berlin Wall Foundation and the Centre for Contemporary History in Potsdam counts at least 140 people who were killed at the Wall or died in connection with it, from Ida Siekmann, who fell from her window on 22 August 1961, to Chris Gueffroy, the last person shot dead while trying to escape, in February 1989.

The Wall was also a stage for the Cold War. In October 1961 American and Soviet tanks faced each other at Checkpoint Charlie. On 26 June 1963 President John F. Kennedy told West Berliners "Ich bin ein Berliner", and on 12 June 1987 President Ronald Reagan stood at the Brandenburg Gate and said "Mr. Gorbachev, tear down this wall!"

By the late 1980s East Germany was stagnating and heavily in debt, and the Soviet Union under Mikhail Gorbachev no longer promised to send tanks to keep its allies' governments in power. In May 1989 Hungary began dismantling its fence with Austria, and in September it let East Germans cross freely. Tens of thousands fled that way or crowded into West German embassies in Prague and Warsaw. At home, the Monday demonstrations in Leipzig grew from a few thousand people to more than 70,000 on 9 October, and the security forces did not fire. Erich Honecker was forced out on 18 October, and on 4 November hundreds of thousands rallied on Alexanderplatz in East Berlin.

The new leadership drafted looser travel rules to relieve the pressure. On the evening of 9 November 1989 Politburo spokesman Günter Schabowski read them out at a televised press conference and, asked when they took effect, answered "immediately, without delay". Crowds gathered at the crossings. At about 11.30 pm the officer in charge at Bornholmer Straße, Harald Jäger, opened the gate, and the other crossings followed during the night. People climbed onto the Wall at the Brandenburg Gate and began chipping pieces off it.

East Germany held its first free election on 18 March 1990, adopted the Deutsche Mark on 1 July and agreed to join the Federal Republic. The two German states and the four wartime Allies signed the Two Plus Four Treaty in Moscow on 12 September 1990, ending the Allies' rights over Germany and fixing its borders, including the Oder–Neisse line with Poland. On 3 October 1990, now German Unity Day, Germany was reunified. Official demolition of the Wall had begun on 13 June 1990; today its course is marked across Berlin by a double row of cobblestones.

Some sections still stand: the 1.3 km East Side Gallery along the Spree, covered in murals; the Berlin Wall Memorial on Bernauer Straße, which keeps a full stretch of the border strip; and a section on Niederkirchnerstraße beside the Topography of Terror museum.