As a Member of Parliament in Weimar,[1] Joseph Joos grew to become one of the leading voices of the Christian Democratic Union in Germany.

After France took over Alsace following the 1919 Treaty of Versailles, Joos decided to remain involved in German politics and became an outspoken opponent of the then nascent National Socialist movement.

In 1938, the Nazi authorities stripped Joos of his German citizenship as Alsatians were not considered reliable citizens in the imminence of a war.

Thanks to his personal background and his credibility with the new German government as well as with the French Resistance, Joos became a prominent advocate for a European Union.

Joseph Joos attended the Weimar National Assembly in January 1919 in his capacity of representative of the Christian Democrats of the Rhein region.