Marshall graduated from Wittenberg University in 1941 with a Bachelor of Arts degree and from the Chicago Lutheran Theological Seminary in 1944.
Kauffman was awarded Doctor of Divinity degrees from both Carthage College and Wittenberg University, in addition to other graduate study at the University of Chicago
He spent three years as the pastor of a California church. He became a professor of Old Testament Interpretation at the Chicago Lutheran School of Theology (now the Lutheran School of Theology at Chicago. Marshall was hired by Muhlenberg College, where he was later appointed as head of the school"s religion department.
He served as president of the Lutheran Illinois Synod until 1968.
Marshall was installed in ceremonies held at Riverside Church in October 1968, with clergymen from around the world in attendance. Marshall was elected to a full four-year term at the biannual convention held in Minneapolis in June 1970, receiving 545 votes out of the 593 cast.
On March 31, 1978, Marshall announced that he would not seek re-election to another term as president, and would instead take a position with the Lutheran World Ministries. He stated that the reasons for his decision were not based on health but reflected his desire for "some new vision to come in".
During his ten years in the office, Marshall led the 3 million-member group and restructured the church"s ministries in the United States and around the world.
He continued his remarks by noting that "we should not exalt our differences, we should work on them". The combined body had 10,500 congregations and 4.8 million members in the United States and the Caribbean by the time of Marshall"s death. Marshall died at age 90 on December 22, 2008 of heart failure in Allentown, Pennsylvania.
He was buried in Burlington, Iowa.