This northern campaign resembled autumn manoeuvres, and was mainly intended to test the value of the new tactics which Germany proposed to use next spring against a more serious foe. It was more realistic to experiment upon Russians than among themselves, and Von Hutier was selected to make the demonstration. The advance began in the last days of August, and on 1 September Von Hutier forced the passage of the Dvina at Uexküll, eighteen miles above Riga, which the Russians abandoned on the following day. Friedrichstadt fell next, and the Russians retired from Jacobstadt on the 21st. The Germans were now across the Dvina on a front of seventy miles, and pushed on towards Wenden, meeting with occasional resistance. But their next experiment was at the expense of the Russian Navy, which was even more demoralized than the Army, and had murdered its officers wholesale. On 12 October the Germans landed a force on the island of Oesel, and within a week had overrun that and the other islands at the mouth of the Gulf of Riga. On the 21st they crossed to the mainland, disembarking a force at Verder opposite Moen Island. There was little to hinder a march on Petrograd, had there been any sufficient inducement. But Petrograd in the hands of the Bolsheviks was worth more to the Germans than in their own; for a German occupation of the capital would have sterilized its miasmic influence over the rest of Russia, and the Germans had only advanced so far in order to get into touch with Finland and establish pro-German governments among the little nationalities of the Baltic littoral. They had, moreover, to economize their shrinking manpower, and their reserves were being called off from all the Eastern fronts to more urgent tasks elsewhere, leaving Russia to stew in its own disintegration.