Rusch served the church and academy in a number of ways. An ordained Lutheran minister, he served on the World Council of Churches (WCC) central committee and the WCC Commission on Faith and Order, as well as the Joint Working Group of the Vatican and World Council of Churches, as well as a leader in Lutheran-Episcopal and Lutheran-Roman Catholic dialogues in the US.
He was also a prolific and distinguished scholar, publishing more than 100 articles and authoring or editing over 20 books, including Toward a Common Future (2019) and, with Richard John Neuhaus, The Pontificate of Benedict XVI: Its Premises and Promises (2009). Rusch had a keen sensitivity and an unwavering respect for religious difference.
Rusch earned his Ph.D. in historical theology from Oxford and taught at Fordham University, Lutheran Theological Seminary at Philadelphia, New York Theological Seminary, Tantur Ecumenical Institute (Jerusalem), and the Angelicum (Rome), in addition serving as an adjunct professor at Yale Divinity School. He first came to Yale in 1999 as lecturer of Lutheran Polity and later had the title lecturer in the History/Polity of the Lutheran Church.
Rusch wrote: “In spite of signs of malaise in the (ecumenical) movement, we cannot overlook the positive steps toward Christian unity that have occurred. … The ecumenical movement calls Christians to be faithful and persist. In this remarkable anniversary year of commemoration—if not celebration—we cannot neglect the urgency of the unity of the church.”