I remember hearing somewhere that armies in the dark ages were oftentimes as small as a few hundred men compared to the thousands of earlier and later periods. Is this true?
Adrian Goldsworthy in his book How Rome Fell - Death of a Superpower (2009) argues that Romans during 3rd and 4th century were unable to field as many soldiers as they did in previous centuries. Battles where emperors participated were won or lost with thousands of soldiers rather than tens of thousands.