Born in Lauchstädt in 1775, Radlof, a linguistic activist, marks the shift from the 17th- and 18th-century tradition of language improvers to the ethnonational paradigm of the Grimm brothers. Radlof was a tireless activist for the German language’s purification and for raising its social and cultural prestige; in an Enlightenment-prescriptive mode, he suggested improvements such as using the southern variants as a normative standard (Trefflichkeiten der südteütschen Mundarten zur Verschönerung und Bereicherung der Schriftsprache, 1811; published soon after his appointment at the Munich court library). Radlof early on adopted Arndt’s moral opposition between German virtue and French vice and correlated this with the linguistic regimes then in force in Europe: French standing for duplicity and (when used in Germany) for self-alienation, German standing for honesty and authenticity. He also at an early stage denounced the dialect divergences between the forms of German as used in various German lands, seeing linguistic and political diffraction as manifestations of a single national malaise and pleading for language convergence as a tool towards political unification and a common front against French hegemony. Grouped the variants which he aimed to embrace in a common German linguistic awareness historically and genealogically into a family tree, in an early instance of the comparative-historical method. In order to map Die Sprachen der Germanen in ihren sämmtlichen Mundarten (1817), he used New Testament biblical texts, documented in many variants from different periods; that method had been used before in the variants of the Lord’s Prayer for all the languages of the Russian Empire, and the parable of the Prodigal Son for the languages and dialects of the Napoleonic Empire (by Coquebert de Montbret, in 1807).

Radlof’s political and scholarly outlook recommended him to the Grimm brothers (and vice versa) but their mutual sympathy ended in a rift over Radlof’s strongly prescriptive and normative stance, and his irritation that Jacob Grimm had appropriated the historical-comparative method in his Deutsche Grammatik – leading to a controversy in 1820. Meanwhile Radlof, who had a less profound historical knowledge than Grimm but a better grasp of dialect variations, had been appointed professor at the Universty of Bonn (1818), where he had published Mustersaal aller teütschen Mundarten, enthaltend Gedichte, prosaische Aufsätze und kleine Lustspiele (1821-22). He sank into obscurity subsequently, with occasional, highly speculative and eccentric publications on the ancient origins of the Germanic nation.