The shallow waters and indented coastlines of the Adriatic did not lend themselves to major marine engagements. The Allied strategy there was mainly one of confinement, particularly after Italy entered the war on the Allied side; the British and French navies wanted to keep the Central Powers contained there, minimizing disruption of the vital supply routes across the Mediterranean and through the Suez Canal. This was exemplified by the establishment of the Otranto barrage across the mouth of the Adriatic, which was successful in preventing the egress of surface vessels, less so with submarines. The Central Powers intermittently went on the offensive, notably in the Austro-Hungarian bombardment of Ancona after Italy entered the war. The challenging environment was conducive to innovation, including a range of modified light aircraft and, most notably, the Italian siluranti, or motor torpedo boats, which twice managed to sink Austro-Hungarian battleships.