T. E. Lawrence’s Undergraduate Dissertation – Page 52

With nothing heavier than a palisade of tree-trunks on the top. Incursions such as those of the Northmen, were in the ninth century the most compelling cause of castle-building. and such hurried raids were better met by earthworks than by the most scientifically planned structure in masonry. Even unskilled workmen could throw up a defensible fortress in a few days, and an earthwork is by no means a thing to be lightly contemned. Caesar had to proceed against one in Britain in most formal fashion, by testudo and agger, and naturally against assailants of the same quality as the defenders such fortresses as Maiden Castle, (Plan 6) or Hambury fort were impregnable. Of those, as late as the time of the Danish invasion of England it can be said "hardly one fell in 20 years of war," and there is no reason for thinking that Alfred's burhs were of exceptional efficiency. Unfortunately the modern confusion in the study of earthworks makes them almost hopeless subjects to date or even to argue about. Certain facts are known historically, such as the construction of burgs by Charles the Great in great numbers ; the fortified bridges and camps of Charles --------------------------------------------------- (1) The Nervii built lines 15 miles long, with a 9 foot vallum and 15 foot ditch, in three hours according to Caesar (d. B.G. V. 42) (2) d. B.G. V. 9.