Short answers, pulled from the story.
Karl Barth is best known for his commentary The Epistle to the Romans, his role in drafting the Barmen Declaration, and his unfinished multi-volume work the Church Dogmatics, published between 1932 and 1967. The Church Dogmatics runs to over six million words and 9,000 pages and is considered one of the longest works of systematic theology ever written.
The Barmen Declaration was a 1934 theological statement rejecting Nazi influence over German Christianity. Karl Barth was responsible for virtually the entire text, with only a single phrase written by someone else. It became a founding document of the Confessing Church, and Barth mailed a copy to Adolf Hitler personally.
Barth was deported from Germany in 1935 after refusing to sign the Oath of Loyalty to Adolf Hitler without modification. He was one of only two professors at the University of Bonn who declined to take the oath, the other being Kurt von Fritz. He returned to Switzerland and took a chair at the University of Basel.
Barth denied being a universalist, writing that he did not believe in universalism but did believe in Jesus Christ as reconciler of all. He argued, however, that Christians were permitted to hope for the salvation of all people as a matter of grace, and he rejected the Calvinist idea that damnation is a certainty for most of humanity.
Charlotte von Kirschbaum was Barth's theological colleague, researcher, and long-time companion who lived in the Barth family home for 37 years. Scholar George Hunsinger wrote that Barth could not have been what he was, or done what he did, without her. Intimate letters released in 2017 by Barth's children revealed a decades-long love relationship between the two.
Karl Barth appeared on the cover of Time magazine on the 20th of April 1962. The cover was a sign that his influence had extended beyond academic and ecclesiastical circles into mainstream American religious culture.