This thesis considers the military effectiveness of the late seventeenth century militia, focusing upon those county forces which took part in the Monmouth Rebellion campaign of 1685.  If the militia were effective then there should be evidence of it fulfilling a set of specified criteria for effectiveness.  After examining the militia's historical purpose and context, as well as its relationship with society, these criteria were defined and then used to test evidence assembled from primary sources. Documents containing information and comments upon the nature, operation and performance of the militia were consulted, including records of contemporary official and personal material held both by local and national record offices.  The results showed the militia to have been militarily effective, thus lending support to the hypothesis that they were more effective than hitherto supposed.  Further research was conducted using information gathered from personal accounts, private papers, letters, financial records, diaries and memoirs held in record offices, libraries and muniment rooms.  These also supported the view that the militia was actually an efficient military organisation, according to the period expectations and demands made of it. The sheer number of references discovered, together with the nature and status of their authors, suggests that modern works have presented an inaccurate view of the militia and its qualities.  In the light of this new evidence, it was concluded that the late seventeenth century militia were effective in contemporary terms, and recommends that current literature be revised