 When the First World War started in 1914 it was the habit of ground troops to fire on all aircraft, friend or foe, so that the need for some form of identification mark became evident.At first the Union Flag was painted under the wings and on the sides of the fuselage.It soon became obvious that at a distance the St George's Cross of the Union Flag was likely to be confused with the Iron Cross that was already being used to identify German aircraft.