[5] In 1906, Kurth was promoted to emeritus status and left the university to take up the position of director of the Belgian Historical Institute in Rome.

In 1873, he was elected president of the Cercle catholique de l'Est, one of the predecessor bodies to the Catholic Party, which Kurth played a role in founding.

Over the summer and autumn of 1915, he gathered testimony of the atrocities, including the killings at Aarschot, but was placed in detention by the Germans in an unheated location.

His work on the atrocities was published posthumously as Le Guet-apens prussien en Belgique ("The Prussian Ambush in Belgium").

Cardinal Désiré-Joseph Mercier wrote in the preface that Kurth, whose family origins were German, was "overwhelmed by the invasion, its iniquity, its atrocities, its sham".

However, Kurth's version of history is notably technical, founded on rigorous principles of historical criticism, extensive mastery of philology and profound knowledge of the sources and other works.