Jürgen Habermas, born to a middle-class family in Düsseldorf, Germany, had a cleft palate at birth that made it difficult for him to learn to speak clearly. He had corrective surgery twice during his childhood and as an adult maintained that his speech disability made him think differently about the importance of communication, and prefer writing over the spoken word. As a teenager, he served in the Hitler Youth and was sent to defend the western front during the final months of World War II. He studied philosophy at universities in Göttingen and Bonn, followed by studies in philosophy and sociology at the Institute for Social Research in Frankfurt under Max Horkheimer and Theodor Adorno. In the 1960s and 70s, Habermas taught at the University of Heidelberg and the University of Frankfurt. In 1971, he was named director of the Max Planck Institute for the Advancement of Science in Starnberg, where he worked until 1983. His magnum opus, The Theory of Communicative Action, was published in 1981. He returned to Frankfurt as director of the Institute for Social Research, and retired in 1993. Habermas was acclaimed as a teacher and mentor to many young political and social theorists and social philosophers. Since his retirement from teaching, he has continued to be an active thinker and writer.