general supposedly entrusted the defence of the Rhine frontier to the Franks and Alamanni, who were Roman foederati, for the time being until the Goths had been driven out of Italy. Furthermore, he interpreted the Frigeridus fragment as showing the Franks being initially successful in preventing the Vandals from crossing the Rhine, but that they could no longer hold them back when the Alans joined the fray. However, Heather (2009) pointed out that the evidence for any Roman military withdrawal from the northwest at this time is weak. Alternative dating – Baynes and Kulikowski A 2000 article by Michael Kulikowski, finding that in traditional historiography "the sequence of events bristles with technical difficulties", bypassed modern historians' accounts, which he found to have depended upon Gibbon and one another, and reanalysed the literary sources. His conclusion was that a date for the mid-winter crossing of the Rhine of 31 December 405 offers a more coherent chronology of events in Belgica, Gaul and Britannia. However, Kulikowski's dating theory, which is a revival of arguments that were put forward by Norman H. Baynes, was forcefully challenged by Anthony Birley. Problems with Prosper's account Kulikowski outlined how 406 came to be selected. The sixth consulship of Arcadius, with Probus as co-consul, corresponds to 406. Prosper noted the invasion of Italy by Radagaisus as the prime event of the previous year, as well as his death, which actually occurred in 406, and he correctly assigned to the next year (407) the usurpation of Constantine III. "The three entries are linked, and together they tell a kind of story", Kulikowski observed. "Prosper was writing a chronicle, and the genre abhorred blank years. Since his chosen genre demanded an entry for each of three years, Prosper simply portioned out his sequence of events, one event to the year. He does the same thing elsewhere in the chronicle". Usurpation of Marcus Kulikowski noted a contradiction between Prosper's date and the assertions made by a fragment of Olympiodorus of Thebes, Zosimus's New History (vi.3.1) and Orosius that the Rhine crossing and the presence of barbarians in Gaul provoked the usurpation of Marcus in Britannia: the latter occurred in the course of 406, thus preceded the 31 December 406 date, and therefore the Rhine crossing must have happened earlier. Kulikowski's proposed date of 31 December 405 places the acclamation of the first of the usurpers in Britannia, which was characterised