These days histories of the later Roman empire are replete with revisionist analyses of the barbarian involvement; it almost seems that political correctness and liberal sensitivities with respect to modern day immigration in Europe are also deeply affecting the interpretation of the past history of Europe, so that nothing negative whatsoever can be said in relation to late Roman immigration. For certain, "blaming" the barbarians in any capacity whatsoever for any involvement in The Fall is right out of fashion.
Halsall sets out his store very early on, declaring that the breakup of the West caused the barbarian migrations and not vice versa. Roman influence didn't stop at the Danube/Rhine/North Sea interface, and the decline of authority on the Empire side created a pull effect across the other side.
However the following 500 plus pages fail to make a convincing argument for this, neither in terms of what was the nature of the pull effect and why it was created by the breakdown of authority, nor indeed why authority began to break down. If there even was any argument at all it must have been so subtle that it frankly passed me by completely.
He certainly feels that the locals willingly and cheerfully entered into deals with the barbarians to hand over power, purely based on the absence of complaints in the contemporary literature about barbarians nicking land. It would have been difficult however for them to argue with the pointy bits of swords and spears, always the basis of authority through the Empire.
That's not to say that this isn't a valuable and thought-provoking book. By reanalysing Halsall questions many of the assumptions passed down and showing them to be on shaky ground; for example, he convincingly argues that the treaty with the Visigoths conferring the status of foederati came many years later than is usually assumed. He even debunks the odd total myth; for example, he traces the oft-quoted "fact" that the Vandals, Alans and Suevi were only able to cross the Rhine in 406 when it was frozen back to a completely fanciful notion originated by Gibbon.
Valuable reading for this period, even if the main thesis presented by the book appears to lack an argument.