Yet they leave no sort of trace in the archaeological records unless they are captured by a Dictaphone or written down by a clerk. The movement of troops on the battlefield may "change the course of history", but this is equally ephemeral from the archaeologist's standpoint. What is a perhaps worse, most organic material are perishable. Everything made of wood hide wool linen grass hair and similar materials will decay and vanish in dust in a few years or centuries, save under very exceptional conditions. In a relatively brief period the archaeological record is reduced to mere scraps of stone bone, glass metal, and earthenware. Still modern archaeology, by applying appropriate techniques and comparative methods aided by a few lucky finds from peat bogs deserts and frozen soils is able to fill up a good deal of the gap.