By law, a certain number of militiamen had to be recruited from among the able-bodied men in each parish. Thus, lists of all those eligible had to be drawn up by the parish constable, and where these survive (between 1757 and 1831) they constitute a veritable census. Along with the "Defense Lists"--the Posse Comitatus of 1798 and the Levee en Masse of 1803-04--and muster rolls of various militia regiments and local forces, these militia lists (in theory) are almost a complete census of the male population. Militias were generally raised on a county basis, and most of these voluminous records are found today in the various county record offices. The fourth edition of this important work is a guide to the location of all such records in the county record offices throughout Britain.