Key Facts
- Duration
- 12–20 October 1917 (9 days)
- Prisoners captured
- 20,000
- Guns captured
- 100
- Islands seized
- Saaremaa, Hiiumaa, Muhu
- Operation type
- Combined air, land, and naval assault
Strategic Narrative Overview
German forces launched combined air, land, and naval operations on 12 October 1917, opening with landings at Tagalaht Bay on Saaremaa after clearing mines and silencing coastal batteries. Saaremaa fell by 16 October. Hiiumaa was captured on 13 October after two initial landing failures. Russian ground forces evacuated Muhu on 20 October. The Russian Baltic Fleet suffered losses at the Battle of Moon Sound and was compelled to withdraw from the Suur Strait.
01 / The Origins
By autumn 1917, Germany sought to press its advantage on the Eastern Front as the Russian Empire disintegrated following two revolutions. The West Estonian Archipelago — comprising Saaremaa, Hiiumaa, and Muhu — dominated the central and northern Baltic Sea strategically. Seizing these islands would threaten Petrograd, neutralise the Russian Baltic Fleet's operational base, and potentially force Russia out of the war entirely.
03 / The Outcome
Germany successfully occupied all three islands by 20 October 1917, capturing approximately 20,000 prisoners and 100 artillery pieces. The Russian Baltic Fleet's forced withdrawal eliminated its ability to contest the archipelago. The operation hastened Russia's strategic collapse on the Eastern Front and contributed to the conditions that led to the Treaty of Brest-Litovsk in March 1918, formally ending Russian participation in the war.
Belligerents & Mobilization Analysis
Side A
1 belligerent
Side B
1 belligerent
Kinetic Engagement Axis
Scroll horizontally to view full axis. Events plotted relatively.