In 1806, during the War of the Fourth Coalition, Grawert commanded an infantry division and participated in the Battle of Jena. After the Treaties of Tilsit, he was appointed Governor-General of Silesia. In this position Grawert managed to win the respect of the French generals and of Napoleon himself. The later requested him as commander of the Prussian Auxiliary Corps which, as part of Jacques MacDonald's X Corps of the Grande Armee, participated in the French invasion of Russia in 1812. Early in the campaign Grawert commanded his corps at Ekau. There he fell off his horse and broke his leg, forcing him to relinquish command to Lieutenant General Ludwig Yorck.