The term 'CLASS SUBMARINE' can be broken down into two parts: ALFA (4 letters) and SUBMARINE. ALFA is a type of SUBMARINE developed by the Soviet Union during the Cold War. It was designed to be a nuclear-powered attack SUBMARINE, capable of carrying up to 24 cruise missiles. The SUBMARINE was also equipped with advanced sonar and radar systems, allowing it to detect and track enemy vessels. The ALFA class submarines were considered to be some of the most advanced submarines of their time.