Berlin’s most interesting subway line and the very one that serves our headquarters
On April 18^th, 1939, the first subway train ran continuously from Neukölln to Gesundbrunnen, connecting the workers' residential districts with the city centre and numerous other express trains along this route. Until then, however, the planning and construction of the underground route had to heed the social and political framework, which is the reason for the long period of 16 years between the start of construction and the commissioning of this line.

The pre-history of the construction of Berlin’s subway
As industrialisation in the expanding metropolis of Berlin progressed faster and faster at the beginning of the 20^th century, the demand for transport increased at the same rapid pace in order to bring the large number of workers to the production sites. Trams and buses alone could no longer cope with this onslaught; mass transportation was needed.
The city and circle lines, as well as the Siemens elevated and underground electric railways, met the criteria but covered only a few of the most in demand transport connections and, particularly in the north-south direction, there were still no efficient connections.
Up until the end of the 19th century, investments in transport infrastructure, and means of transport and operations were exclusively privately organised but, at the beginning of the 20^th century, the municipal administrations in the expanding cities recognised the macrosocial task of housing and transport development. Exclusively profit-oriented and privately financed transport projects could no longer meet the political requirements to manage urban growth. As the first autonomous city within the area of what is today Berlin, wealthy Schöneberg was able to open its own underground railway in 1910 (the Schöneberg Underground).
However, Berlin was also planning urban rapid transit systems. On three routes, the urgent need for elevated and underground railways was recognised. These were connections from western Wedding through Friedrichstrasse to Tempelhof and Rixdorf (today Neukölln), a connection from Moabit past the Lehrter, Potsdamer and Görlitzer termini to Treptow, and a line from eastern Wedding via Alexanderplatz to Rixdorf.
However, there was a lack of both capacity and financial resources to implement all three lines within a reasonable timeframe. In the end, private capital was used again. The line from Gesundbrunnen to Rixdorf appeared to be the most profitable. Two companies applied for a concession to build and operate a railway along this route. These were the "Continentale Gesellschaft für elektrische Unternehmungen" from Nuremberg, which built the suspension railway in Barmen-Elberfeld (today Wuppertal), and the "Allgemeine Elektricitäts-Gesellschaft" (AEG) from Berlin which, until then, mainly had experience with the electrification of trams.  

16 years until commissioning
AEG finally prevailed over the suspension railway project with its plans for an elevated and underground railway. It is not clear whether this had more to do with the concern that a suspended railway would be an eyesore in the city centre, or to what extent the numerous political and social contacts of the Berlin-based Rathenau family (Emil Rathenau, father of the later Foreign Minister Walter Rathenau, was the founder and chairman of the board of directors of AEG) influenced this decision. In 1912 - while political conditions in the German Empire were still stable - the contract between the city of Berlin and AEG was signed. In the spring of 1914, construction was started by AEG-Schnellbahn AG, a subsidiary founded specifically for this purpose.
However, the project quickly ran into difficulties. Just a few months after the start of construction, war was declared in Europe and the First World War began. While at the beginning work progressed according to plan, the shortage of skilled workers and especially of engines to pull the carriages soon made itself felt. Prices for building materials rose, if they were still even available; the profitability of the construction company was slipping ever further out of reach. In 1918, while the AEG Schnellbahn was reducing work to the bare minimum, shooting was already going on over the construction sites.
In the stormy times of the November Revolution, the abdication of Emperor Wilhelm II and repeated violent uprisings and coup attempts, it was impossible to imagine that the rapid transit system would be completed in an orderly fashion, not least from the point of view of economic efficiency.
AEG-Schnellbahn AG finally informed the city of Berlin that the deadlines agreed in 1912 could not be met, whereupon the city of Berlin sued for fulfilment of the contract. The lawsuit, which dragged on for years, was decided in favour of the city of Berlin in 1923. As a result of rising inflation, AEG-Schnellbahn AG saw no other choice but to go into liquidation.
In this way, the city of Berlin was awarded a rapid transit construction site without any compensation.
But Berlin, too, was initially not in a position to continue the construction of the railway. It was only with the stabilisation of the economy and society after overcoming the inflation of the mid-1920s that Berlin had room to manoeuvre. The so-called Golden Twenties began. In 1926, construction was continued by the municipal Nordsüdbahn AG, with a partly modified route.
However, after rapid construction progress and the first partial openings from 1927 onwards, further expansion plans came to a standstill again with the world economic crisis of 1929. The important junction at Gesundbrunnen station and thus the continuous connection from Neukölln to Gesundbrunnen could only be realised in 1930. However, the connection in the south to Hermannstrasse station, and thus to the circle line, failed; work on this subway station, which was completed in its shell state, had to be stopped.

The era of bunker installations
In the "1,000 years" between 1933 and 1945, ambitious expansion plans followed, but not even the connection to the Hermannstrasse circle line, for which only a few hundred metres of tunnel were required, was completed. Instead, numerous sidings and unused tunnel remains were converted into air raid shelters and bunkers. Today, Berlin Underworlds has its headquarters in one of these facilities at Gesundbrunnen station, which explains our strong connection to the history of Berlin's "most exciting" subway line.

From subway line D to the U8
But even after overcoming the damage caused during the Second World War, subway line D, as it was called then, could still not assume a "normal" everyday life. Suddenly, the subway no longer ran under district borders, rather under the border of two political blocs, which were hostile towards each other. Under the "Iron Curtain", and even after the curtain became the Wall in 1961, the subway continued to run - but only as a shadow of its former self. Although line D still connected Neukölln and Gesundbrunnen, it passed under Berlin Mitte at Alexanderplatz without stopping. After six stations in Neukölln and Kreuzberg were closed, six ghost stations under East Berlin followed before two more in Wedding, at Voltastrasse and Gesundbrunnen.
When "walled-in" West Berlin had enough financial means at its disposal again, the construction of the underground railway was forged ahead with. The U8, as it has been called since the changeover to numbers on March 1^st, 1966, was also taken into consideration. It was planned to connect the Märkisches Viertel to the underground network but, until this point, financial means were only sufficient for construction as far as Wittenau S-Bahn station. They fell just two stations short of their goal! With the reunification of Berlin in 1989/1990, the U8 experienced its halcyon days as a politically important transport link and achieved its largest passenger volume ever. For many people, the U8 became their gateway to the West. Trains were overcrowded, people flocked to West Berlin on the few restored rapid transit connections, many with shopping streets or department stores as their destination. Karstadt department store, located on the southern end of the railway right beside Hermannplatz station, was as overcrowded as the trains. Only now, after all stations in East Berlin were gradually reopened and the southern connection to the circle line was established, could the subway line between Gesundbrunnen and Neukölln consistently perform the tasks assigned to it almost 100 years before.

Authors: Dietmar Arnold and Axel Mauruszat, May 3^rd, 2009