As editor of the scholarly volumes accompanying the Rhineland-Palatinate state exhibition "Das Reich der Salier 1024-1125" in Speyer in 1992 and through numerous other publications, Weinfurter proved himself to be one of the best experts on the era of the Salian emperors.
In 1999, he published a biography of Henry II, followed by books and numerous essays on the Salian period, the Hohenstaufen dynasty, the road to Canossa and medieval imperial history.
With his academic teacher Odilo Engels, he edited four volumes of the Series episcoporum ecclesiae catholicae occidentalis (1982, 1984, 1991, 1992), a prosopography of the early and high medieval bishops.
[26] The Bamberg conference in June 1996 on the continuities and discontinuities in the reigns of Otto III and Henry II, organized with Bernd Schneidmüller, proved particularly fruitful for his biography.
The account was at the same time the first volume of a new series of publications (medieval research) edited by Schneidmüller and Weinfurter, which aims to "take up innovative questions of modern mediaevistics in their entire breadth and, if possible, to interest a wider audience in them.
In his biography, Stefan Weinfurter particularly emphasized the increased expectation of the end times and the biblical guiding figure Moses for Henry's reign.
"[38] According to Weinfurter, Henry's behavior, on the other hand, "can only be explained from his very individual conception of the legitimacy, task, and function of his kingship, which is rooted in his ruler personality.
[42] After an overview of the source material and the early Carolingians, Weinfurter treated Charlemagne's reign not chronologically, but systematically according to levels of action (wars, domestic politics, family, educational reform, church policy, and emperorship).
[45] With his thesis of "unification", which runs through all twelve chapters of the account, Weinfurter means "the interpretive sovereignty in religious and moral behavior", "the unambiguity of language, argumentation and temporal order" as well as that of "political, military and ecclesiastical organization.
[48] In 1987 he presented an edition of the Geschichte der Eichstätter Bischöfe by Anonymus Haserensis based on the only surviving medieval manuscript (Diözesanarchiv Eichstätt, MS 18) of the late 15th century.
[54] As part of the Collaborative Research Center 933 "Materiale Textkulturen" and in cooperation with Heidelberg University Library, a conference was held in Lorsch Monastery in 2012.
[57] In another paper he concluded, based on linguistic parallels, that the Vita Arnoldi, a letter of Archbishop Arnold to Wibald of Stablo from spring 1155, and the mandate of Emperor Frederick I (DFI 289) have the same author - that is, Gernot.
[58] Weinfurter's student Stefan Burkhardt presented the Vita Arnoldi archiepiscopi Moguntinensis (The biography of Archbishop Arnold of Selenhofen of Mainz) in an annotated new edition with translation in 2014.
[66] 900 years after the death of Emperor Henry IV, a symposium was held in May 2006 at the site of his Burial ground in Speyer by the Salisches Kaisertum und neues Europa.
The starting point was the question of whether a relevant change in the political and conceptual order configurations of the empire took place in Frederick I's time and what role the events at the Peace of Venice played in this.
[75] For Weinfurter, in an article published in 2002, the failure of negotiations between Henry V and Pope Paschal II in 1111 and the Peace of Venice in 1177 were turning points in history.
Weinfurter concluded that both times the configurations of order converging on the ruler's authority were weakened to such an extent that the connection to the development of monarchies in Europe finally broke off.
In 1993, together with Hanna Vollrath, he published 23 contributions to a Festschrift for Odilo Engels on the occasion of his 65th birthday about the city and diocese of Cologne in the empire of the Middle Ages.
The fall of the lion is no longer judged as the result of a plan single-mindedly pursued by Barbarossa, but rather the emperor appears as a "driven" of the princes in the deprivation of Henry's power.
For him, Adelheid "took a unique key role for the Ottonian emperorship and appears virtually as the decisive figure in the mediation of the Italic-imperial traditions to the Saxon court.
Starting with the formulation sacro imperio et divae rei publicae consulere from a document of Barbarossa from 1157, he traced the development of the idea of empire under Emperor Frederick I.
In Speyer in May 2008, together with Bernd Schneidmüller and Wojciech Falkowski, he organized a scientific conference on ritualization of political will formation in the high and late Middle Ages in comparison between Poland and Germany.
[96] In addition, Weinfurter examined the punishment of dog carrier based on the works of Otto of Freising, Widukind of Corvey, Wipo, and the vita of Archbishop Arnold of Mainz.
[97] Weinfurter's study Der Papst weint, published in 2010, illustrated how Pope Innocent IV repeatedly wept loudly and publicly at the Council of Lyon in 1245 when deposing Emperor Frederick II, thereby emphasizing the inevitability of his actions.
[107] Two comprehensive volumes edited by Weinfurter, Bernd Schneidmüller, and Alfried Wieczorek were published to accompany the exhibition "The Hohenstaufen and Italy" at the Reiss-Engelhorn Museums in Mannheim, which ran from September 19, 2010, to February 20, 2011.
The contributions deal with the scope of action of the Wittelsbach dynasty and their rule in the Palatinate and cover the period from 1200 to the end of the War of the Succession of Landshut in 1504/05.
For the European Foundation Imperial Cathedral of Speyer, Weinfurter co-chaired the fourth scientific symposium on "King Rudolf I and the Rise of the House of Habsburg in the Middle Ages" with Schneidmüller in April 2018.
Weinfurter's last project before his death was the work on the large state exhibition of the Rhineland-Palatinate General Directorate for Cultural Heritage "The Emperors and the Pillars of their Power.
According to Jörg Peltzer, the assertion of the papal claim to represent Christ alone on earth, the resulting changes in the sacral character of the emperorship, and the strengthening of princely self-understanding as bearers of the empire are three developments of long-term significance shaped by Weinfurter.
[121] Today's image in historiography of the East Frankish-German ruler Henry II is determined by Weinfurter's biography published in 1999 and his accompanying studies.