The historical study of Philip of Swabia began in 1852 with the monograph "König Philipp der Hohenstaufe" by Heinrich Friedrich Otto Abel, who made no secret of his sympathies for Philip. Eduard Winkelmann's Yearbooks of German History ("Jahrbücher der Deutschen Geschichte") under Philip of Swabia and Otto IV (1878) became the standard reference work of later historiography. With 541 closely described pages, they are the most detailed account of the Hohenstaufen to date. In his work, Winkelmann was more sober than Abel. It was based on a statement by Johann Friedrich Böhmer who called Philip "the best of all Hohenstaufen". Winkelmann wrote about Philipp in his preface through "a faithful defense of imperial rights against the rebellious principality and against the Pope, against Denmark and against France [... as the true German king", he was "attractive as a person, as a king to be counted among the best and most capable ”. In 1866 Wilhelm Grotefend published his dissertation. Unlike Winkelmann and Abel, he passed a damning verdict on Philip. To him, he was regarded as an "dependent, weak personality with a smooth form and graceful appearance, but without nobility of disposition." The decisive factor for this judgment was that Philip didn't fight energetically enough for his kingship and, through the alliance with the French king, granted this influence over the Holy Roman Empire. In addition, he had allowed to an arrogant Pope and selfish princes to make too many concessions.