After the start of the First World War and the unsuccessful pursuit of the German ships "Goeben" and "Breslau" in August 1914, the B-class submarines were transferred to the Dardanelles area in mid-September to prevent any breakout attempt by the German ships. After the arrival of the larger and more modern E-class submarines in early 1915, the B-class boats began to return to Malta. After the Kingdom of Italy joined the Allies in May 1915, the B-class submarines in the Mediterranean were transferred to Venice to reinforce Italian forces in the northern Adriatic. "B9", and were the first to arrive in Venice on 11 October and "B9" made their first patrol a week later. She saw no targets and returned to Venice three days later. The five British submarines made a total of 13 patrols off the Austro-Hungarian coast before the end of 1915, hampered by bad weather and drifting mines, followed by 13 more in the first two months of 1916.