His father, another Julius Petersen (1835-1909), was a senior lawyer and judge from Landau (Pfalz) who, in addition, served between October 1881 and April 1883 as a member of the German Reichstag (parliament).

[3][4] The younger Julius Petersen attended secondary school at the "Nikolaischule", far away to the east in Leipzig, to where the family had evidently relocated in connection with his father's judicial appointment to the I. Strafsenat" (loosely, "first criminal bench") at the German High Court.

[1] He moved on to his university-level education in 1897, studying German philology, art history and philosophy at the universities of Lausanne, Munich, Leipzig and Berlin.

In North America he was also able to deepen his friendship with Kuno Francke at nearby Harvard University, a long established professor of German Culture and History, who is reported greatly to have respected Petersen's academic abilities.

[8][10] He transferred again in 1914, this time to the newly opening "Goethe University" at Frankfurt am Main, as an ordinary [i.e. full and permanent] Professor of Modern German Language and Literature.

By setting out his own teaching programme in this way, Petersen invited his audience to infer an intention and ability to mediate a synthesis between philology and the history of thought, and thereby between traditionalists and modernists.

[1] Six years later, with the political and social context transformed by war and revolution, this earned him an invitation to fill the professorial teaching chair in the History of Modern German Literature at Berlin's Friedrich Wilhelm University formerly occupied by his old tutor, Erich Schmidt.

[1][12] During his professorship at Berlin of more than twenty years' duration, Julius Petersen undertook several major overseas lecture tours, at least some of which were undertaken in his capacity as president, between 1926 and 1938, of the Goethe Society.

[1] His advocacy of compromise in the so-called philological "methodology dispute" of the 1920a may not have been conceptually innovative, but through the various assignments he undertook and the various editions he oversaw of the works of icons of German literature such as Lessing, Goethe, Jean Paul and Schiller, Petersen did become the most prominent and perhaps influential of the nation's "new Germanisticists".

[1] Petersen was much criticised, especially after 1945, for the way in which he used his influence as a popular and respected Berlin university professor to pull the mainstream study of Germnanistics into line with dogmas of National Socialism which were at best bizarre or offensive, and some of which proved desperately dangerous after their noisiest exponents took power in 1933.

In 1934 he became the producer-editor of Euphorion, a long established literary journal which now changed its title to "Dichtung und Volkstum" and adopted a starkly nationalistic tone.

It seems likely that he became a member of the government backed "Nationalsozialistischer Deutscher Dozentenbund" (loosely, "National Socialist Lecturers League") if only in order to retain his job at the university, but there is no indication that he ever joined the party itself.

He took the opportunity to stress his assessment that Goethe's sense of patriotism corresponded not to quiet contemplation but to "active self-determination to stay true to oneself, self-assertion and the constant striving for self-improvement", and thereby to the "ideology of the Third Reich".

[13] More recently, arguments have surfaced that it was precisely because of his known intellectual support for the Hitler regime that, in respect of his personal situation, Petersen felt able to take significant risks on a human level.

Others, unable to afford to escape or unwilling to accept that the Nazis believed their own propaganda, stayed in Germany and were, in vast numbers, murdered at the direction of the government a few years later.

[2] Two of his better known students, identified by the authorities as Jewish or half-Jewich, whom Petersen helped to escape the country after their situation in Germany became unacceptably dangerous, were Richard Alewyn and Charlotte Jolles.

It was still unpublished when he died, but it proved possible to add some final detailed corrections from the manuscripts and publish it posthumously in 1944, expended to include an introduction, by Erich Trunz, whose own academic career took off, in some respects, at the point at which Petersen's had ended.