He successfully completed their science course and on 26 January 1812 was promoted to the rank of ensign in a quartermaster unit and a secondment to the 24th Infantry Division.

For his actions at Maloyaroslavets he was awarded the Order of Saint Vladimir 4th class, with swords and bow and finally, from 3 to 10 November, at Krasnoi.

Grand Duke Konstantin Pavlovich appointed him to his personal staff and Dannenberg also received promotions to lieutenant and captain along with the Order of St Anne 2nd class.

During the Crimean War, Dannenberg was given command of Russian troops on the Danube front where he lost the Battle of Oltenitza.

When the fighting moved to the Crimea, he was given command of part of the Russian forces there, which unsuccessfully assaulted the British positions during the Battle of Inkerman.