Arnims's editorial work was increasingly affected by the Napoleonic Wars. Upon the Prussian defeat in the 1806 Battle of Jena–Auerstedt, he followed the royal court to Königsberg, where he joined the circle of Prussian reformers around Baron vom Stein. In 1807 he moved back to Weimar and Kassel, where he visited the Brothers Grimm, and finally to Heidelberg. He and Brentano completed the second and third volume of their folk song collection and from 1808 together with Joseph Görres published the important romantic "Zeitung für Einsiedler" (Newspaper for Hermits) in Heidelberg in 1808. The Heidelberg Romanticist circle also included Tieck, Friedrich Schlegel, Jean Paul, Justinus Kerner, and Ludwig Uhland.