Key Facts
- Duration
- 1915–1918 (approx. 3 years)
- Peak vessel count
- Over 200 vessels
- Strait blocked
- Strait of Otranto, between Brindisi and Corfu
- Effectiveness vs. surface ships
- Effective — no Austro-Hungarian surface escape
- Effectiveness vs. submarines
- Little or no effect on Cattaro-based submarines
Strategic Narrative Overview
The Allies deployed a continuous patrol line of drifters, destroyers, and other vessels stretching across the strait, which grew to over 200 ships at its peak. The barrage successfully denied Austro-Hungarian surface warships passage into the Mediterranean. However, the blockade proved far less capable against submarines: Austro-Hungarian U-boats based at Cattaro regularly slipped through, continuing to menace Allied shipping throughout the war.
01 / The Origins
Following Italy's entry into the First World War in 1915, the Allies sought to contain the Austro-Hungarian Navy within the Adriatic Sea. The Strait of Otranto, the narrow southern exit of the Adriatic between Brindisi, Italy, and the Greek island of Corfu, was identified as the critical chokepoint. Control of this passage was essential to prevent Austro-Hungarian warships from threatening Allied naval and supply operations across the broader Mediterranean theatre.
03 / The Outcome
The barrage remained in operation until the end of the First World War in 1918. With Austria-Hungary's defeat and the dissolution of its navy following the armistice, the strategic rationale for the blockade ceased. The operation demonstrated both the potential and the limitations of static naval barriers — effective against surface vessels but largely unable to stop submarine infiltration through the same contested waters.
Belligerents & Mobilization Analysis
Side A
1 belligerent
Side B
1 belligerent