In 1766 Valckenaer succeeded Hemsterhuis in the Greek chair. The intimacy between the two colleagues was only broken by Valckenaer's death in 1785, and stood the test of common candidature for the office (an important one at Leiden) of 12th Librarian of Leiden University, in which Ruhnken was successful. Ruhnken's later years were clouded by severe domestic misfortune, and by the political commotions which, after the outbreak of the war with England in 1780, troubled the Netherlands without ceasing, and threatened to extinguish the University of Leiden.