It was realised early in the development of aerial warfare that there was a need to identify your enemy as quickly as possible. The aircraft had brought war into a whole new domain – the sky, but it had also introduced a faster kind of warfare. Aircraft from that time were capable of speeds of up to 250 kph and this meant less time to determine who was ‘friend or foe’.

At first it was thought that applying national markings to aircraft would help, and they did, once aircraft were engaged in close combat. The problem was how to identify your enemy when they were further away, preferably before they had spotted you. Achieving this would provide a tactical advantage, but it relied on the aircrew’s ability to recognise the shape of an aircraft at distance.