 With the outbreak of war with the Ottoman Empire in 1787, Prince Grigory Potemkin asked Möller to join his field army based out of Ekaterinoslav, and assist in the planning of besieging Ochakov.After the strategic fortress was taken, Möller was awarded with both the Orders of St. Andrew and St. George in the 2nd class alongside the title of baron.During the campaign of 1790, he was given command of his own field corps assigned to seize the fortress of Kiliya.