In heraldic achievements, the helmet or helm is situated above the shield and bears the torse and crest. The style of helmet displayed varies according to rank and social status, and these styles developed over time, in step with the development of actual military helmets. In some traditions, especially German and Nordic heraldry, two or three helmets (and sometimes more) may be used in a single achievement of arms, each representing a fief to which the bearer has a right. For this reason, the helmets and crests in German and Nordic arms are considered to be essential to the coat of arms and are never separated from it.