The V-2 (, "Retribution Weapon 2"), with the technical name Aggregat 4 (A4), was the world's first long-range guided ballistic missile. The missile, powered by a liquid-propellant rocket engine, was developed during the Second World War in Germany as a "vengeance weapon" and assigned to attack Allied cities as retaliation for the Allied bombings against German cities. The rocket also became the first artificial object to travel into space by crossing the Kármán line with the vertical launch of MW 18014 on 20 June 1944.