Under the influence of Hermann Baumgarten and Heinrich von Treitschke, he oriented himself towards modern and contemporary history and habilitated in 1887 in Berlin with the latter on Gaspard II de Coligny and the Assassination of Francis, Duke of Guise, supplemented by the essays he had submitted up to that time.
Further stations in his academic career were professorships at Leipzig in 1894, Heidelberg University in 1901, Hamburg Scientific Foundation in 1907, the US, where he was a visiting professor in 1912, and, from 1913, Munich.
From 1910, Marcks was co-editor of the Historische Zeitschrift alongside his friend Friedrich Meinecke, together with whom he was also appointed Historiographer of the Prussian State [de] in 1922.
His main work influenced by this was a highly influential two-volume biography of Otto von Bismarck (published in 1909 and 1915), which celebrated the first Reich Chancellor as the consummator of German history and with which Marcks showed himself to be a herald of the authoritarian power state.
[4] The Third Reich regarded Marcks as a contemporary re-establishment of the Bismarck Empire, and so in 1935 he became an honorary member of Walter Frank's National Socialist Reichsinstitut für Geschichte des neuen Deutschlands [de].