Ernst Reuter returned to Germany in November 1946. Against his hope for a higher position according to his qualifications the SPD's leadership asked him to go to Berlin where he resumed his position as the city counselor for traffic and public services, a position known to him from the 1920s. Under the difficult conditions of the post-war period Reuter led the re-organization of the vital services gas, water, and electricity in the quadripartite city. After the mayor Otto Ostrowski, a member of the SPD, resigned from office, Ernst Reuter was elected his successor by the city council assembly at the beginning of June in 1947. Yet, his inauguration was prevented by a Soviet veto at the Allied Kommandantura. Instead, Luise Schroeder, also a SPD-member, conducted the mayor's affairs for more than a year.
After the beginning of the Soviet blockade of Berlin in June 1948 the "prevented" mayor Ernst Reuter soon became the most important voice for freedom, democracy, and self-determination. His speech in front of the ruins of the Reichstag building on September 9, 1948, ("People of the world, look upon this city!") made him a symbol for the perseverance of the Berlin people against the Soviet aggression. In the elections for the city council assembly on December 5, 1948, (taking place only in the Western part of the city) Reuter's Social Democrats won 64.5 percent of the votes and became the strongest party.