But it was not long before both the Alamanni and the Franks again became troublesome in the Rhine valley. Under the year 357, in the history of Ammianus Marcellinus, there is a vivid description of the struggle of Julian to regain from the Alamanni the cities on the Lower Rhine which the latter had occupied, as in the time of Probus, within the Roman province of Lower Germany. After the decisive battle of Strasburg, Julian crossed the Rhine at Mayence and laid waste the country between the Maine and the Rhine, 'plundering the wealthy farms of their crops and cattle, and burning to the ground all the houses, _which latter in that district were built in the Roman fashion_.'[415] He then restored the fortress of Trajan which protected this part of the 'Limes.' The next year, the Salian Franks having taken possession of Toxandria, on the Scheldt, Julian pounced down upon them and recovered possession, and then set himself 'to restore the fortifications of the cities of the Lower Rhine, and to _establish afresh the granaries which had been burned, in which to stow [p287] the corn usually imported from Britain_.'[416] This was the occasion on which, according to Zosimus, 800 vessels, more than mere boats, were employed in going backwards and forwards bringing over the British corn, thus proving both the extent of British agriculture and the close connexion between Britain and the province of Lower Germany. «Bucenobantes deported into Britain.» The aggressions of the Alamanni, however, continued, and again we find Ammianus Marcellinus describing how, at the close of a campaign, Valentinian, in A.D. 371, deported into Britain the Bucenobantes, a tribe of the Alamanni from the east banks of the Rhine, immediately north of Mayence. He made them elect Fraomarius as their chief, and then, giving him the rank of a tribune, sent him with his tribe of Alamannic soldiers to settle in Britain, as probably Crocus or Erocus had been sent before him.[417] «The policy a settled one, and long continued.» This policy of planting colonies of German colonists--even whole clans under their petty chiefs--in the Belgic provinces and Britain, with the double object of keeping up the supply of corn for the empire and soldiers for the legions, was therefore steadily adhered to for several generations. And a further proof of the extent to which the system was carried turns up later in the numerous cohorts of Læti mentioned by Ammianus,[418] and in the '_Notitia_,'[419] as having been drawn from these colonies [p288] and placed as garrisons all over Gaul and Germany, but especially on the banks of the Rhine.