Only
Zosimus, who wrote around 500 AD, gives information about the Salians before 357 AD. He describes them as a people detached or separated from the Franks (), who had been expelled from their own country by the
Saxons and settled at some time prior to 357 AD on the large island of Batavia, between two branches of the Rhine. Although Batavia was within the boundaries once governed by the Romans, the Salians were governing it by 357 AD. He describes the Saxons who forced them there as the strongest of all the barbarians dwelling near that Rhine delta region. A more contemporary source,
Ammianus Marcellinus, also associated the Salians with the Franks, calling them Franks "whom custom calls the
Salii". The Romans had inconsistent and incomplete control of the Rhine delta since the
crisis of the third century. The population and agricultural activity had decreased dramatically, and the Romans had given it up as an area for normal taxation and governance. Some modern scholars believe the Salians attacked by Julian to be descendants of the Frankish who
Constantius Chlorus allowed to remain in Batavia around 293-294 AD, when the Romans reasserted themselves there after the revolt of
Carausius. They were probably also descended from the Franks who were later allowed to settle in Texandria by the brother of Constantius II, his co-emperor
Constans, already in 342 AD, after fighting there in 341 AD. Julian also associated the usurper
Magnentius, who had killed Constans and ruled the region in 350-353 AD, with the Franks and Saxons of this region. At the
Battle of Mursa Major in 351 AD in present day Croatia many Roman soldiers with Frankish and Saxon backgrounds died fighting in this Roman civil war. Like Magnentius himself one of his main commanders
Silvanus, who defected to Constantius, had Frankish ancestry. He was given the task of rebuilding defences in Gaul, but killed as a rebel in 355 AD. In the same year Julian was given the rank of
Caesar, and assigned to rule Gaul under his cousin Constantius, and rebuild the Rhine defences against the Franks and Saxons who Magnentius had apparently coordinated with. Julian's campaign against the Salians was at least partly triggered by a Roman concern with bringing grain shipments from Britain safely up the Rhine, without being impeded by the Salians and other Rhine delta peoples.
Libanius (Oration 18.83) an orator who corresponded with Julian and wrote his funeral oration, emphasizes the problems caused by barbarians on the Rhine blocking such grain shipments. Both Libanius and Zosimus (3.5) reported that Julian, wanting to supply inland areas where cultivation had been ruined by other conflicts, built a fleet on the Rhine and began shipping grain up the river to Roman cities. In his letter to the Athenians Julian however complained of the disgrace that despite quick construction of a large fleet, the praetorian prefect
Florentius sent to Gaul by
Constantius II in 357, "promised to pay the barbarians a fee of two thousand pounds weight of silver in return for a passage". Julian decided that this payment to the barbarians should not be made, and instead he marched against these barbarian tribes - specifically the Salians and Chamavi. His account of the campaign itself is compressed: "I received the submission of part of the Salian tribe, and drove out the Chamavi and took many cattle and women and children. And I so terrified them all, and made them tremble at my approach that I immediately received hostages from them and secured a safe passage for my food supplies". The conflict between Julian and Florentius itself appears to be part of a set of related disputes for fiscal control of northern Gaul, and Julian may have been disrupting a prior state of affairs which entailed integration of the Chamavi and the Salians into imperial systems of military taxation and supply. Another turn of events which triggered this campaign was the entry of the Chamavi into the Roman region south of the Rhine. According to Zosimus the barbarians of the delta region were losing all hope because of Julian's policies on the Rhine, and they were expecting the complete destruction of everyone who still lived there. Apparently in reaction to this, the Saxons sent a faction of a Saxon people called the "Quadi" (by which he apparently meant the Chamavi), into the land held by the Romans. According to Zosimus, these "Quadi" (Chamavi) used boats on the Rhine to get around Frankish tribes who effectively protected the Roman frontier, and into the Roman river delta, where they expelled the Salians from Batavia and established a base for themselves. Ammianus simply says that the Salians dared to start building homes within Roman territory in Texandria, and that the Chamavi attempted to do something similar. together with the specialized guerrilla forces of
Charietto who, according to Zosimus (3.6), were brought into the conflict because the Chamavi did not dare direct engagement with the Romans, and chose instead to make stealthy attacks into the Roman lands. Charietto's approach worked, and he captured the son of the Chamavi king alive, and this was later revealed to the Chamavi king in the final negotiations which Julian conducted via translator while standing on a boat in the river. The Salians were then brought into Roman units defending the empire from other Frankish raiders. The
Notitia dignitatum, listing Roman military units at the end of the 4th century mentions the
Salii iuniores Gallicani based in
Hispania, the
Salii seniores based in Gaul. There is also record of a
numerus Saliorum. The names of these units do not necessarily mean that they were made up of Salians, but the units were created by Julian. Zosimus (3.8) writing around 500 AD says, apparently using military lists of his own time, that "Caesar stationed the Salians, a portion of the Quadi, and some of those on the island of Batavia in military units, which even in our time still seem to be preserved ()". ==Later mentions==