The author of the Chronicle of Fredegar written in the 7th century claimed that the Franks came originally from Troy and quoted the works of Vergil and Hieronymus, and the Franks are mentioned in those works, by Hieronymus. The chronicle describes Priam as a Frankish king whose people migrated to Macedonia/Albania after the fall of Troy. In Macedonia, the Franks then divided. The European Franks reached Francia under King Francio, just as Romulus went to Rome. Fredegar stated that Theudemer, named king of the Franks by Gregory, was descended from Priam, Friga and Francio.

Another work, the Gesta, described how 12,000 Trojans, led by Priam and Antenor, sailed from Troy to the River Don in Russia and on to Pannonia, which is on the River Danube, settling near the Sea of Azov. There they founded a city called Sicambria. (The Sicambri were the most well-known tribe in the Frankish homeland in the time of the early Roman empire, still remembered though defeated and dispersed long before the Frankish name appeared.) The Trojans joined the Roman army in accomplishing the task of driving their enemies into the marshes of Mæotis, for which they received the name of the Franks (meaning “savage”). A decade later the Romans killed Priam and drove away Marcomer and Sunno, the sons of Priam and Antenor, and the other Franks.

The major primary sources on the early Franks include the Panegyrici Latini, Ammianus Marcellinus, Claudian, Zosimus, Sidonius Apollinaris and Gregory of Tours.

The Franks are first mentioned in the Augustan History, a collection of biographies of the Roman emperors. None of these sources present a detailed list of which tribes or parts of tribes became Frankish, or concerning the politics and history, but to quote James (1988, p. 35):

A Roman marching-song joyfully recorded in a fourth-century source, is associated with the 260s; but the Franks’ first appearance in a contemporary source was in 289. The Chamavi were mentioned as a Frankish people as early as 289, the Bructeri from 307, the Chattuarri from 306–315, the Salii or Salians from 357, and the Amsivarii and Tubantes from c. 364–375.

In 288 the emperor Maximian defeated the Salian Franks, Chamavi, Frisians and other Germanic people living along the Rhine and moved them to Germania inferior to provide manpower and prevent the settlement of other Germanic tribes. In 292 Constantius, the father of Constantine I defeated the Franks who had settled at the mouth of the Rhine. These were moved to the nearby region of Toxandria. Eumenius mentions Constantius as having “killed, expelled, captured and kidnapped” the Franks who had settled there and others who had crossed the Rhine, using the term nationes Franciae for the first time.

It seems likely that the term Frank in this first period had a broader meaning, sometimes including coastal Frisians.

The Franks were described in Roman texts both as allies (laeti) and enemies (dediticii). About the year 260 one group of Franks penetrated as far as Tarragona in present-day Spain, where they plagued the region for about a decade before they were subdued and expelled by the Romans. In 287 or 288, the Roman Caesar Maximian forced a Frankish leader Genobaud and his people to surrender without a fight. Maximian then forced the Salians in Toxandria (the present Low Countries) to accept imperial authority, but was not able to follow on this success by reconquering Britain.

The Life of Aurelian, which was possibly written by Vopiscus, mentions that in 328, Frankish raiders were captured by the 6th Legion stationed at Mainz. As a result of this incident, 700 Franks were killed and 300 were sold into slavery. Frankish incursions over the Rhine became so frequent that the Romans began to settle the Franks on their borders in order to control them.

The Franks are mentioned in the Tabula Peutingeriana, an atlas of Roman roads. It is a 13th-century copy of a 4th or 5th century document that reflects information from the 3rd century. The Romans knew the shape of Europe, but their knowledge is not evident from the map, which was only a practical guide to the roads to be followed from point to point. In the middle Rhine region of the map, the word Francia is close to a misspelling of Bructeri. Beyond Mainz is Suevia, the country of the Suebi, and beyond that is Alamannia, the country of the Alamanni. Four tribes at the mouth of the Rhine are depicted: the Chauci, the Amsivarii (‘Ems dwellers’), the Cherusci and the Chamavi, followed by qui et Pranci (‘who are also Franks’). This implies that the Chamavi were considered Franks. The Tabula was probably based on the Orbis Pictus, a map of twenty years’ labour commissioned by Augustus and then kept by the Roman’s treasury department for the assessment of taxes. It did not survive as such. Information about the imperial divisions of Gaul probably derives from it.

The Salians were first mentioned by Ammianus Marcellinus, who described Julian’s defeat of “the first Franks of all, those whom custom has called the Salians,” in 358. Julian allowed the Franks to remain in Texuandria as fœderati within the Empire, having moved there from the Rhine-Maas delta. The 5th century Notitia Dignitatum lists a group of soldiers as Salii.

Some decades later, Franks in the same region, possibly the Salians, controlled the River Scheldt and were disrupting transport links to Britain in the English Channel. Although Roman forces managed to pacify them, they failed to expel the Franks, who continued to be feared as pirates.

The Salians are generally seen as the predecessors of the Franks who pushed southwestwards into what is now modern France, who eventually came to be ruled by the Merovingians.

Gregory of Tours reported that small Frankish kingdoms existed during the fifth century around Cologne, Tournai, Cambrai and elsewhere. The kingdom of the Merovingians eventually came to dominate the others, possibly because of its association with Roman power structures in northern Gaul, which the Frankish military forces were apparently integrated into to some extent. Aegidius, was originally the magister militum of northern Gaul appointed by Majorian, but after Majorian’s death apparently seen as a Roman rebel who relied on Frankish forces. Gregory of Tours reported that Childeric I was exiled for 8 years while Aegidius held the title of “King of the Franks”. Eventually Childeric returned and took the same title. Aegidius died in 464 or 465. Childeric and his son Clovis I were both described as rulers of the Roman Province of Belgica Secunda, by its spiritual leader in the time of Clovis, Saint Remigius.

Clovis later defeated the son of Aegidius, Syagrius, in 486 or 487 and then had the Frankish king Chararic imprisoned and executed. A few years later, he killed Ragnachar, the Frankish king of Cambrai, and his brothers. After conquering the Kingdom of Soissons and expelling the Visigoths from southern Gaul at the Battle of Vouillé, he established Frankish hegemony over most of Gaul, excluding Burgundy, Provence and Brittany, which were eventually absorbed by his successors. By the 490s, he had conquered all the Frankish kingdoms to the west of the River Maas except for the Ripuarian Franks and was in a position to make the city of Paris his capital. He became the first king of all Franks in 509, after he had conquered Cologne.

Merovingian society had a militarised nature. The Franks called annual meetings every Marchfeld (1 March), when the king and his nobles assembled in large open fields and determined their targets for the next campaigning season. The meetings were a show of strength on behalf of the monarch and a way for him to retain loyalty among his troops. In their civil wars, the Merovingian kings concentrated on the holding of fortified places and the use of siege engines. In wars waged against external foes, the objective was typically the acquisition of booty or the enforcement of tribute. Only in the lands beyond the Rhine did the Merovingians seek to extend political control over their neighbours.

Immediately beneath the Frankish king in the military hierarchy were the leudes, his sworn followers, who were generally ‘old soldiers’ in service away from court. The king had an elite bodyguard called the truste. Members of the truste often served in centannae, garrison settlements that were established for military and police purposes. The day-to-day bodyguard of the king was made up of antrustiones (senior soldiers who were aristocrats in military service) and pueri (junior soldiers and not aristocrats). All high-ranking men had pueri.

Tactically, the Merovingians borrowed heavily from the Romans, especially regarding siege warfare. Their battle tactics were highly flexible and were designed to meet the specific circumstances of a battle. The tactic of subterfuge was employed endlessly. Cavalry formed a large segment of an army, but troops readily dismounted to fight on foot. The Merovingians were capable of raising naval forces: the naval campaign waged against the Danes by Theuderic I in 515 involved ocean-worthy ships and rivercraft were used on the Loire, Rhône and Rhine.