September of the Italian battleship in Brindisi harbour by Italian-speaking Austro-Hungarian saboteurs. Over 450 were killed. In late September, the Allies established the Otranto Barrage, an attempt to blockade the entrance to the Adriatic Sea at the Strait of Otranto. December In early December, the French submarine ran aground off the Bojana River estuary due to bad navigation, and was sunk by the Austrian destroyer Warasdiner. The cruiser Helgoland and three destroyers sortie against the Otranto Barrage from 5–22 December and performed reconnaissance off the Albanian coast and San Giovanni di Medua. They sank an Italian picket boat, three steamships loaded with ammunition and two armed schooners en route to Northern Albania. The light cruiser SMS Helgoland and five Tatra-class destroyers left Cattaro and headed for Durazzo late on 28 December 1915. While on passage the French submarine was rammed by the cruiser SMS Helgoland, and finally sunk by gunfire from the destroyer . Early the next day, the Austrians squadron opened fire on Durazzo targets, sinking some small ships. Then they ran into a minefield. The destroyer Lika was sunk and Triglav was damaged. She was taken in tow and the Austrian force sailed slowly to north. An allied force had already sailed from Brindisi, with the aim to intercept them. It was composed of the British light cruisers HMS Dartmouth and Weymouth, the Italian light cruisers RN Quarto and Nino Bixio and five French destroyers. In support of the retreating force, the Austrians despatched the armoured cruiser SMS Kaiser Karl VI and the light cruiser Novara from Cattaro. Early in the afternoon of 29 December, the forward Allied ships came into action with the retreating Austrian light squadron, which was still only halfway home. The Triglav was abandoned and scuttled and a long-range gunnery duel was fought throughout the afternoon. SMS Tatra was damaged but the Austrian light force was able to reach Cattaro safely. 1916 Austrian submarines sank or damaged a number of ships in 1916. U-11 captured the Italian hospital ship King Albert on 18 January at San Giovanni di Medua. sank the French destroyer on 16 March at Durazzo. On 8 June, U-5 torpedoed and sank the Italian troop transport Principe Umberto at Linguetta. Later, U-5 fought a French-Italian destroyer group to a stalemate on 2 August, and torpedoed the Italian Q-Ship Pantelleria south of Taranto on August 14. On 15 September 1916, the two