The requirements were eventually made official in November 1956 with General Operational Requirement 339 (GOR.339), which was issued to various aircraft manufacturers in March 1957. This requirement was exceptionally ambitious for the technology of the day, requiring a supersonic all-weather aircraft that could deliver nuclear weapons over a long range, operate at high level at Mach 2+ or low level at Mach 1.2, with STOL or possible VTOL performance. The latter requirement was a side-effect of common battle plans from the 1950s, which suggested that nuclear strikes in the opening stages of war would damage most runways and airfields, meaning that aircraft would need to take off from "rough fields" such as disused Second World War airfields, or even sufficiently flat and open areas of land.