Carl Erdmann (1898–1945)

Educational Background

As a young man Erdmann appeared to be destined for a career in the Church, but at the age of 21 he changed direction and began to study History in Munich under Paul Joachimsen. Following his time in Portugal (see below), he became a research student at the University of Würzburg. He was awarded his doctorate in 1926.

Career Notes

During the early years of his postdoctoral academic career Erdmann worked at what is now the German Historical Institute in Rome. In 1932 he completed the manuscript of his study of the origins of early crusading ideology; a revised version of the text was published in 1935.

Erdmann went on to work at the Monumenta Germaniae Historica, where he was engaged in the production of critical editions of texts relating to the eleventh-century reform movement and the so-called ‘Investiture Controversy’. It was here that he developed his expertise in the epistolary culture of the Middle Ages.

Erdmann’s subsequent career progression was hampered by the fact that he was unwilling to support the political changes that were taking place around him; according to Baldwin and Goffart, ‘since he had made no secret of his distaste for the new National Socialist regime in Germany, his academic appointments were withdrawn and additional distinctions denied him’ (Erdmann 1977: p ix). Erdmann remained at the Monumenta Germaniae Historica until 1943, after which time he was conscripted to the German army. He died of illness in 1945 whilst serving as an interpreter in the Balkans.

A more detailed biographical study of Erdmann’s life, written in German by Friedrich Baethgen, can be found as a preface to a collection of Erdmann’s work published posthumously: C Erdmann, Forschungen zur Ideenwelt des Frühmittelalters, ed F Baethgen (Berlin, 1953), pp viii-xxi.

Interests, Influences and Methodologies

Erdmann’s interests in the crusades can probably be traced to the number of years he spent in the early 1920s working in Portugal as a private tutor; it was during this time that he made use of the country’s libraries and archives to gather the information necessary for him to write his doctoral thesis on medieval Portugal.

Erdmann’s early training as a theologian undoubtedly influenced his intellectual approach to crusading ideas, although one modern scholar has noted of The Origin of the Idea of Crusade that it was ‘the most unideological treatment of an ideology’ and that Erdmann ‘was clearly not interested in the devotional aspects of his subject’ (Riley-Smith: p 18). Erdmann’s experiences working with Paul Kehr on the Papsturkunden series and at the Monumenta Germaniae Historica were also of great significance to his academic development; Giles Constable has written that Erdmann ‘combined the tradition of German intellectual history or Geistegeschichte, which emphasized the ideas underlying the observable events of history, with a rigorous training in source-criticism’ (Constable: p 11).

On a more personal level, Erdmann was obviously extremely sensitive to the political circumstances of his day. In 1935, his book on crusading ideas contained the following dedication, which included a less than subtle criticism of life under the Third Reich:

To the memory of my father
who lost a professorship at Dorpat [Tartu] in 1893
for remaining true to his mother-tongue
and of my brothers who gave their lives in 1914 and 1916
this book is dedicated with unshaken faith in the
future of the german spirit

As Marcus Bull has noted, Erdmann’s work ‘has been interpreted as coded criticism of German militarism under the National Socialists’ (Bull: pp 355-6).

Contribution to Crusader Studies

The significance of Erdmann’s The Origin of the Idea of Crusade has been immense. Giles Constable has written that ‘More than any other single work written in the twentieth century, Erdmann’s book changed the direction of crusading studies’ (Constable: p 10), whilst Jonathan Riley-Smith wrote that ‘Most academic works have a shelf life of not much more than twenty years, but Erdmann’s monograph still attracts serious discussion after sixty’ (Riley-Smith: p 17). Although some of the book’s main arguments have been subject to considerable scrutiny by recent scholars such as Marcus Bull, John France, John Gilchrist and Jonathan Riley-Smith, no modern study of crusading ideology can be undertaken effectively without reference to Erdmann’s approaches or his conclusions.

In addition to his work on crusading ideas, Erdmann’s work on medieval epistolary culture should not be overlooked; several of the critical editions he produced, for example, remain the standard texts used by modern scholars.

Select Publications

Papsturkunden in Portugal (Berlin, 1927).

Das Papsttum und Portugal im ersten Jahrhundert der portugiesischen Geschichte (Berlin, 1928).

‘Das Wappen und die Fahne der römischen Kirche’, Quellen und Forschungen aus italienischen Archiven und Bibliotheken, vol 22 (1930-31), pp 227-255.

Die Entstehung des Kreuzzugsgedankens (Stuttgart, 1935).

Die Briefe Heinrichs IV (Leipzig, 1937).

Studien zur Briefliteratur Deutschlands im XI Jahrhundert (Leipzig, 1938).

The Origin of the Idea of Crusade, trans MW Baldwin and W Goffart (Princeton, NJ, 1977).


MG Bull, ‘The Roots of Lay Enthusiasm for the First Crusade’, History, vol 78 (1993), pp 353-72.

G Constable, ‘The Historiography of the Crusades’, The Crusades from the Perspective of Byzantium and the Muslim World, ed AE Laiou and RP Mottahedeh (Washington, DC, 2001), pp 1-22.

J France, ‘Holy War and Holy Men: Erdmann and the Lives of the Saints’, The Experience of Crusading, Volume One: Western Approaches, ed M Bull and N Housley (Cambridge, 2003), pp 193-208.

J Gilchrist, ‘The Erdmann Thesis and the Canon Law, 1083–1141’, Crusade and Settlement: Papers Read at the First Conference of the Society for the Study of the Crusades and the Latin East and Presented to R.C. Smail, ed PW Edbury (Cardiff, 1985), pp 37-45.

JSC Riley-Smith, ‘Erdmann and the Historiography of the Crusades, 1935–1995’, La primera cruzada, novocientos anos después: el concilio de Clermont y los origines del movimiento cruzado, ed L Garcia-Guijarro Ramos (Madrid, 1997), pp. 17-29.


Written by: Dr William Purkis