Advances were made in nearly every aspect of naval warfare, most notably with aircraft carriers and submarines. Although aeronautical warfare had relatively little success at the start of the war, actions at Taranto, Pearl Harbor, and the Coral Sea established the carrier as the dominant capital ship in place of the battleship. In the Atlantic, escort carriers proved to be a vital part of Allied convoys, increasing the effective protection radius and helping to close the Mid-Atlantic gap. Carriers were also more economical than battleships because of the relatively low cost of aircraft and their not requiring to be as heavily armoured. Submarines, which had proved to be an effective weapon during the First World War, were anticipated by all sides to be important in the second. The British focused development on anti-submarine weaponry and tactics, such as sonar and convoys, while Germany focused on improving its offensive capability, with designs such as the Type VII submarine and wolfpack tactics. Gradually, improving Allied technologies such as the Leigh light, hedgehog, squid, and homing torpedoes proved victorious over the German submarines.