Short answers, pulled from the story.
Being and Time (Sein und Zeit), published in 1927, is Heidegger's magnum opus and is widely considered one of the most significant works of modern philosophy. In it, he introduced the concept of Dasein to describe the distinctive character of human existence and developed his analysis of "being-in-the-world."
Yes. Heidegger joined the Nazi Party on the 1st of May 1933, shortly after being elected rector of the University of Freiburg on the 21st of April 1933. He retained his party membership until 1945 and signed the Vow of Allegiance of the Professors of the German Universities and High-Schools to Adolf Hitler in November 1933.
Dasein, a German compound meaning "being-there," is Heidegger's term for the distinctive kind of being that humans have. It refers to a living being through its activity of "being there" in the world, characterized by a pre-ontological understanding of being that shapes all experience. Heidegger analyzed Dasein as "being-in-the-world," emphasizing involvement and engagement rather than physical containment.
The Black Notebooks, written between 1931 and the early 1970s and published in 2014, contain explicit anti-Semitic passages. One entry invokes the concept of "world Judaism" drawn from the Protocols of the Elders of Zion and Hitler's Mein Kampf. Another argues that Jews had "promoted the very reasoning by which they were now being attacked." Recent research has confirmed a deep connection between these notebooks and volkisch antisemitism.
Edmund Husserl, the founder of phenomenology, was Heidegger's teacher and a major early influence. Aristotle, mediated through Catholic theology and Franz Brentano, shaped his fundamental ontology. Wilhelm Dilthey's concept of hermeneutics, Soren Kierkegaard's treatment of anxiety and mortality, and the poetry of Friedrich Holderlin were central to his development. Friedrich Nietzsche occupied several lecture series in the 1930s and 1940s.
On the 23rd of September 1966, Heidegger gave an interview to Der Spiegel magazine in which he defended his involvement with the Nazi Party, agreeing to its publication only after his death. It appeared on the 31st of May 1976, five days after he died, under the title "Only a God Can Save Us." He claimed his rectorate was an attempt to protect the university from politicization and that he broke with Nazism in 1934, claims contradicted by the eyewitness account of his former student Karl Lowith.