||Although impressively armed and armoured, the capital ships that provided the might of the large European navies in the early 20th century were particularly vulnerable to small, speedy torpedo boats. The torpedo boat destroyer was conceived to counter this threat. Fast and manoeuvrable, the destroyer became a potent threat in its own right - not only was it more than a match for lurking torpedo boats but it could also attack the enemy's capital ships with its own torpedoes. In line with technological developments in naval warfare, the destroyer's role expanded during the Second World War to also provide protection against submarines and air attack. After the Second World War, the requirement for a torpedo attack vessel declined and the destroyer's primary role became that of an anti-submarine and anti-aircraft escort.