He realized his vision of economic and political integration with the German reunification and was one of the architects of modern Europe. He presided over several institutions, a role he combined with writing for numerous leading publications as well as lecturing. He was Deputy Chancellor of Germany for 18 years and an acting Member of Parliament until 1998.

In 2000, he founded his own consultancy, was President of the German Council of Foreign Relations from 2001 - 2003 and was Honorary Professor at The Freie Universität Berlin as well as at Peking University. He was Honorary Senator of the Deutsche Akademie der Naturforscher Leopoldina at Halle (Saale).