Thachulf was placed in charge of the Sorbian March in 849 with the title of dux Sorabici limitis, giving him military command over the counts with lands bordering the Sorbs.
On account of his knowledge of Slavic customs, he was petitioned by the Sorbs with the offer of hostages for peace to protect them from the warmaking of Ernest, Duke of Bavaria, but he had been wounded in battle the day before the arrival of the Slav embassy and so could not be of assistance.
According to the Annales Fuldenses, in 858, a Reichstag held at Frankfurt under Louis the German sent three armies to the eastern frontiers to reinforce the submission of the Slavic tribes.
Carloman was sent against Great Moravia, Louis the Younger against the Obodrites and Linonen, and Thachulf against the Sorbs, who were refusing to obey him.
The armies of Carloman and Louis set out in July, but it is uncertain if Thachulf ever undertook a campaign, as the Sorbs rose in rebellion late in that year and do not appear to have been restless beforehand.