Militia (English)
The obligation to serve in the militia in England derives from a common law tradition, and dates back to Anglo-Saxon times. The tradition was that all able-bodied males were liable to be called out to serve in one of two organisations.These were the posse comitatus, an ad hoc assembly called together by a law officer to apprehend lawbreakers, and the fyrd, a military body intended to preserve internal order or defend the locality against an invader. The latter developed into the militia, and was usually embodied by a royal warrant. Obviously, service in each organisation involved different levels of preparedness.
Read more about Militia (English): Sixteenth and Seventeenth Centuries, Militia in The English Empire, Political Issues, Eighteenth Century and The Acts of Union