Konrad Adenauer
Leader in Cologne

As a devout Catholic, he joined the Centre Party (German: Deutsche Zentrumspartei or just Zentrum) in 1906 and was elected to Cologne's city government in the same year. In 1909, he became Vice-Mayor of Cologne, an industrial metropolis with a population of 635,000 in 1914. Avoiding the extreme political movements that attracted so many of his generation, Adenauer was committed to bourgeois decency, diligence, order, Christian morals and values, and was dedicated to rooting out disorder, inefficiency, irrationality and political immorality. In 1917, he was unanimously elected as Mayor of Cologne for a 12-year period, and re-elected in 1929.

During World War I, he worked closely with the army to maximize the city's role as a rear base of supply and transportation for the Western Front. He paid special attention to the civilian food supply, enabling the residents to avoid the worst of the severe shortages that beset most German cities during 1918–1919. In 1918, he invented a soy-based sausage called the Cologne sausage to help feed the city. In the face of the collapse of the old regime and the threat of revolution and widespread disorder in late 1918, Adenauer maintained control in Cologne using his good working relationship with the Social Democrats. In a speech on 1 February 1919 Adenauer called for the dissolution of Prussia, and for the Prussian Rhineland to become a new autonomous Land (state) in the Reich. Adenauer claimed this was the only way to prevent France from annexing the Rhineland. Both the Reich and Prussian governments were completely against Adenauer's plans for breaking up Prussia. When the terms of the Treaty of Versailles were presented to Germany in June 1919, Adenauer again suggested to Berlin his plan for an autonomous Rhineland state and again his plans were rejected by the Reich government.

He established a good working relationship with the postwar British military authorities, using them to neutralize the workers' and soldiers' council that had become an alternative base of power for the city's left wing. During the Weimar Republic, he was president of the Prussian State Council from 1921 to 1933, which was the representation of the provinces of Prussia in its legislature.

A major debate had occurred within his Centre Party since 1906 regarding the question of whether it should "leave the tower" (i.e. allow Protestants to join, becoming a multi-faith party) or "stay in the tower" (i.e. continue to be a Catholic-only party). Adenauer was one of the leading advocates of "leaving the tower", which led to a dramatic clash at the 1922 Katholikentag, the annual meeting of German Catholics under the presidency of Adenauer. Cardinal Michael von Faulhaber publicly admonished Adenauer for wanting to take the Zentrum "out of the tower".

In mid-October 1923, the Chancellor Gustav Stresemann announced that Berlin would cease all financial payments to the Rhineland and that the new currency Rentenmark, which had replaced the now worthless Mark would not circulate in the Rhineland. To save the Rhineland economy, Adenauer opened talks with the French High Commissioner Paul Tirard in late October 1923 for a Rhenish republic in a sort of economic union with France which would achieve Franco-German reconciliation, which Adenauer called a "grand design". At the same time, Adenauer clung to the hope that the Rentenmark might still circulate in the Rhineland. Adenauer's plans came to naught when Stresemann, who was resolutely opposed to Adenauer's "grand design", which he viewed as borderline treason, was able to negotiate an end to the crisis on his own.

In 1926, the Zentrum suggested Adenauer becoming Chancellor, an offer that he was interested in but ultimately rejected when the German People's Party insisted that one of the conditions for entering into a coalition under Adenauer's leadership was that Gustav Stresemann stay on as Foreign Minister. Adenauer, who disliked Stresemann as "too Prussian," rejected that condition.
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