He is the author of Winfrid-Bonifatius und die christliche Grundlegung Europas, the authoritative biography of Saint Boniface.
A member of the Katholischer Studentenverein Arminia Bonn, one of Germany's oldest Catholic student societies, he wrote his PhD dissertation under the direction of Wilhelm Levison, Die päpstlichen Legaten in Frankreich vom Vertrage von Meersen (870) bis zum Schisma von 1130 (1934).
In 1936, he published an essay on Alexis de Tocqueville in the Munich-based Catholic periodical Hochland, founded by Carl Muth.
[1] The essay, in its discussion of liberty, justice, and law, was a veiled critique of Nazi Germany;[2] in the "remarkable" essay he cites de Tocqueville, "I have always loved liberty; all my thoughts lead me to the conviction that without it there can be no moral or political greatness.
His son, Rudolf Schieffer, likewise a historian of the middle ages, was president of the MGH from 1994 to 2012.