Arensburg was once a powerful fortress, where the German Bishop Osnabriuksky was based in 1341. For centuries the inhabitants of Ösel Island were known as pirates, but during the Northern War of 1708–1711, and after a plague and famine, the fortress of Arensburg fell to the Russians on 26 September 1710. Emperor Peter I made Arensburg an advanced position in the Baltic, but he was not the only one to appreciate the importance of Moon Sound. During the Swedish-Russian War in 1809 the English supporting Sweden used the northern part of Moon Sound as an anchorage. During the two campaigns of the Crimean War in 1854–55 the English fleet used the Moon Sound archipelago as an anchorage, where they were poised as a threat to St Petersburg. Throughout the First World War the islands of Dagö and Ösel held great significance. With the islands remaining as Russian possessions, the Russian Imperial Navy could still outflank the Germans in the Riga Gulf and had the option of staging a landing on the Kurland coast behind the German lines, or of bombarding the German shore positions more or less at will, which they had done since 1915. From their support bases in the Riga Gulf and Moon Sound the Russian destroyers and Russian and English submarines could penetrate into the middle and western Baltic, striking at German trade routes with Sweden. The Baltic Islands and the Riga Gulf were again pivotal for naval warfare in the Baltic. With the islands in German hands the Riga Gulf, and therefore the German Army rear, would be secure, and the facilities at Riga could be utilized as a supply base to further the German offensive. The Russian ‘Forward Position’, the outer defences of the Finnish Gulf, would be under threat. The continued German offensive and the perceived threat to St Petersburg would increase pressure on the Russian government to conclude peace, and with the conclusion of a negotiated peace vast resources of German men and equipment would be freed to join the battle in the west against America, France and the British Empire.
With all due consideration, orders for the attack on the Baltic Islands were issued on 18 September 1917, and read:
For the domination of the Riga Gulf and the security of the flank of the East Army, a combined attack by the land and sea forces is to take the Islands of Ösel and Moon, and the use of the Greater Moon Sound is to be denied to the enemy sea forces.
The operation was code named ‘Albion’ and the following day the troops entrained for the port of Libau. The Army forces consisted of the reinforced 42nd Division, commanded by General von Estorff, and the 2nd Infantry Cyclist Brigade, together with artillery, pioneers, a wireless section and transport column. In total the Landing Corps consisted of around 23,000 men, 5,000 horses, 1,400 vehicles, 150 machine-guns, 54 guns, 12 mortars and munitions and provisions for thirty days. To convey the Landing Corps to their assault beaches in Tagga Bay, on the northwest coast of Ösel, a transport fleet of nineteen steamers was assembled. It was to be the largest combined operation undertaken by the Germans so far during the war. To support the operation the most modern units of the High Sea Fleet were detached and were formed into the Special Unit of the Baltic. The composition of the Special Unit was as follows:
Chief of Special Unit: Vizeadmiral Schmidt
Chief of Staff: Kapitän zur See Levetzow
Flagship: Moltke.
III Battle Squadron
Commander:Vizeadmiral Behncke
König, Bayern, Grosser Kurfürst, Kronprinz, Markgraf
IV Battle Squadron
Commander: Vizeadmiral Souchon
Friedrich der Grosse, König Albert, Kaiserin, Prinzregent Luitpold, Kaiser
II Reconnaissance Group (II AG)
Commander: Kontreadmiral Reuter
Königsberg, Karlsruhe, Nürnberg, Frankfurt, Danzig
VI Reconnaissance Group (VI AG)
Commander: Kontreadmiral Hopman
Kolberg, Strassburg, Augsburg, Blitz, Nautilus
Torpedoboats
I FdT (Führer dur Torpedoboote or Leader of Torpedoboats):
Kommodore Heinrich
Flagship: Emden
II Torpedoboat Flotilla (10 boats)
VI Torpedoboat Flotilla (11 boats)
VIII Torpedoboat Flotilla (11 boats)
X Torpedoboat Flotilla (11 boats)
7th Torpedoboat Half Flotilla (7 boats)
U-Flotilla Kurland
6 U-boats.
Sperrbrechergruppe (literally Barrier-breaker Group)
Rio Pardo, Lothar, Schwaben, Glatz
II Minesweeper Flotilla
3rd Minesweeper Half Flotilla
4th Minesweeper Half Flotilla
8th Minesweeper Half Flotilla
3rd S-Half Flotilla (S- denotes a ‘picket’ or anti-submarine unit)
S-Flotilla of the Baltic
Netbarrier Unit of the Baltic
Fleet Train.
Appointed to lead the Special Unit was the hitherto commander of the I Battle Squadron, Vizeadmiral Ehrhard Schmidt. He was an excellent choice. Vizeadmiral Schmidt had begun the war as commander of the IV Battle Squadron, stationed in the Baltic. This led to him being appointed commander of the first attack on the Riga Gulf in August 1915. The campaign lasted from 8 to 21 August. The first attempt to break in to the gulf failed because of the insurmountable mine barriers. A continuation of the attack led to a German force entering the gulf for a short period on 19 August. Prinz Heinrich came to the conclusion that a recurrence of the break-in attempt
Would only make sense when we could remain in the Gulf. For this purpose it is necessary for the Army to occupy Riga and the mouth of the Dvina. Then the possession of the Gulf can be facilitated, but nevertheless would require considerable naval forces. Only the capture of Ösel and Dagö will simplify the operation and provide an anchorage for the large ships, and also provide opportunities for us to approach the fortified points of the Finnish Gulf.
Riga fell in September 1917 and the situation now allowed the Germans to prosecute their attack plans.
The Russians had long perceived the threat to the Baltic Islands and as early as August 1914 the Fleet Commander, Admiral H O Essen, had said:
Today the 1st Torpedoboat Division was sent to Moon Sound and Riga Gulf, and workbegan on installing batteries for the protection of Moon Sound. I attach great value to the maintenance of communications with the islands of Ösel and Dagö. The occupation of the latter by the enemy would deprive us of advanced observation posts and aviation stations and would entail the loss of Moon Sound.
Theoretically the Riga Gulf and islands were reasonably well protected. Ösel was defended by three infantry regiments, the 425th, 426th and 472nd, who together with the coastal batteries had a strength of around 24,000 men. Tagga Bay was protected by Battery No 45 with four 15.2cm guns at Cape Hundsort and Battery No 46, likewise with four 15.2cm guns, at Cape Ninnast. Work on these batteries had been started on 10 December 1916 and they were completed in April 1917. On Dagö, Battery No 34 was constructed at Serro, a little west of the village of Emmast. It comprised four 120mm guns taken from Amur class monitors and had been completed in early 1916. Dagö was defended by a further two batteries at Cape Tachkona. Battery No 38, of four 15.2cm guns, was mounted at Cape Simpernes and Battery No 39, at Cape Tachkona, consisted of four 12 inch guns. Battery No 37 at Cape Dirhamn consisted of four 15.2cm guns, which, like those of Battery No 38, were also taken from Amur class gunboats. The southern entrance to the Moon Sound was also well protected with batteries. Five 254mm pieces that were originally intended for Nargon Island on the ‘Central Position’ were sent to Moon Island and were installed as Battery No 36 near Woi. However, only two guns could be mounted on concrete bases and the remaining three were mounted on wooden bases. This battery was ready on 5 July 1915. Battery No 32, between the villages of Woi and Resse, consisted of four 15.2cm pieces and was ready on 13 September 1915. A battery on the mainland side, on the island of Werder, completed the southern Moon Sound entrance defences. This battery, No 33, comprised four 15.2cm guns.