The war broke out in Europe in 1939. It had erupted in Asia two years earlier. Hitler invaded Poland, and the Soviet Union organised a counterattack. This officially started the war. The Allied Powers began bombing Berlin heavily in 1943. In 1945 the city was attacked by 1250 US 4-engine bombers. Between 1939 and 1945 Germany weakened progressively. The Soviets converged on Berlin on several fronts in 1945. The Germans fought till the end, refusing to surrender. On April 30, 1945, Hitler committed suicide in his bunker. By that time most of the city was in Allied hands. Before the war ended, around a third of the buildings in Berlin had been destroyed by Allied air strikes and street brawls. The so-called Stunde Null ( Zero Hour) was a turning point in the history of the country. This term referred to the capitulation of the Nazi government on May 8, 1945.

Consequently, Berlin and the greater area were divided into four sectors by the Allied Powers under the London Protocol, which was signed in 1944. Each sector was under the authority of a different power – the US, Britain, France, and the Soviet Union respectively. This division formed the basis of the decision to erect the Berlin Wall. After the division, the Americans, the French, and the British started making efforts to unite their sectors into a federal state. The Russians felt they didn't deserve such treatment, as the Soviet Union had suffered the highest number of war casualties. What's more, the western powers undertook a currency reform without Soviet approval, and the US refused to grant reparations from West German industrial zones to the Soviets. As a result, in 1948 the USSR blocked ground access to West Berlin, which is known today as the Berlin Blockade, with the hope to take control over Berlin's territory. The blockade lasted almost a year. Throughout this time the western powers made efforts to arrange supplies to west Berlin via the so-called Berlin Airlift.

The next turning point in the history of Berlin was the June 17 Uprising. As many as 60 construction workers in East Berlin went on strike on June 16, 1953 demanding lower work quotas. As mentioned, a general strike took place the next day. It swiftly turned into a riot, which East Berlin police were unable to suppress. Soviet troops were called in. They faced resistance from angry crowds throughout East Germany, as the protests had spread like wildfire by that time. Over a hundred people were killed. The stretch of Unter den Linden Blvd. on the western side of Brandenburg Gate was renamed 17th June Strasse to commemorate this event. In West Germany June 17 was declared a national holiday.