The primary sources for Frankish military custom and armament are Ammianus Marcellinus, Agathias, and Procopius, the latter two Eastern Roman historians writing about Frankish intervention in the Gothic War.
Writing of 539, Procopius says: At this time the Franks, hearing that both the Goths and Romans had suffered severely by the war . . . forgetting for the moment their oaths and treaties . . . (for this nation in matters of trust is the most treacherous in the world), they straightway gathered to the number of one hundred thousand under the leadership of Theudebert I and marched into Italy: they had a small body of cavalry about their leader, and these were the only ones armed with spears, while all the rest were foot soldiers having neither bows nor spears, but each man carried a sword and shield and one axe. Now the iron head of this weapon was thick and exceedingly sharp on both sides, while the wooden handles was very short. And they are accustomed always to throw these axes at one signal in the first charge and thus to shatter the shields of the enemy and kill the men. Agathias, says: The military equipment of this people [the Franks] is very simple. . . . They do not know the use of the coat of mail or greaves and the majority leave the head uncovered, only a few wear the helmet. They have their chests bare and backs naked to the loins, they cover their thighs with either leather or linen. They do not serve on horseback except in very rare cases. Fighting on foot is both habitual and a national custom and they are proficient in this. At the hip they wear a sword and on the left side their shield is attached. They have neither bows nor slings, no missile weapons except the double edged axe and the angon which they use most often. The angons are spears which are neither very short nor very long they can be used, if necessary, for throwing like a javelin, and also in hand to hand combat.

The Frankish realm was united again in 613 by Chlothar II, son of Chilperic. Chlothar granted the Edict of Paris to the nobles in an effort to cut down on corruption and unite his vast realm under his authority. After the militarily successful reign of his son and successor Dagobert I, royal authority rapidly declined under a series of kings traditionally known as rois fainéants. By 687, after the Battle of Tertry, the chronicler could say that the mayor of the palace, formerly the king's chief household official, "reigned." Finally, in 751, with the approval of the papacy and the nobility, the mayor Pepin the Short deposed the last Merovingian king, Childeric III, and had himself crowned, inaugurating a new dynasty, the Carolingians.
In the late sixth century, during the wars instigated by Fredegund and Brunhilda, the Merovingian monarchs introduced a new element into their militaries: the local levy. A levy consisted in all the able-bodied men of a district who at the call had to report for military service. The local levy applied only to a city and its environs. Initially only in certain cities in western Gaul, in Neustria and Aquitaine, did the kings possess the right or power to call up the levy. The commanders of the local levies were always different from the commanders of the urban garrisons. Often the former were commanded by the counts of the districts. A much rarer occurrence was the general levy, which applied to the entire kingdom and included peasants (pauperes and inferiores). General levies could also be made within the still-pagan trans-Rhenish stem duchies at the bequest of a monarch. The Saxons, Alemanni, and Thuringii all had the levy and it could be depended upon by the Frankish monarchs until the mid-seventh century, when the stem dukes began to sever their ties to the monarchy. Radulf of Thuringia called up the levy for a war against Sigebert III in 640.

It was highly ritualistic and many daily activities centred around the multiple deities, chiefest of which may have been the Quinotaur, a water-god from whom the Merovingians were reputed to have derived their ancestry. Most of the pagan gods were associated with local cult centres and their sacred character and power were associated with specific regions, outside of which they were neither worshipped nor feared. Most of the gods were "worldly", possessing form and having concrete relation to earthly objects, in contradistinction to the transcedent God of Christianity.

Archaeologically, Frankish paganism has been observed in the burial site of Childeric I, where the king's body was found covered in a cloth decorated with numerous bees or flies. The symbolism of these insects is unknown.

Though a sizeable portion of the Frankish aristocracy quickly followed Clovis in converting to Christianity, the conversion of the whole of the people under Frankish rule required a considerable amount of time and effort - in some places two centuries or more. Early efforts towards organized resistance were quickly squelched: the Chronicle of St. Denis relates that, following Clovis' conversion, a number of devout pagans, unhappy with this turn of events, rallied around Ragnachairus (or Ragnachar), a powerful figure who had played an important role in Clovis' initial rise to power. Though the text remains unclear as to the precise pretext, Clovis soon had Ragnachairus thrown in chains and then executed. As for the remaining pockets of resistance, they were overcome region by region - primarily due to the work of the quickly expanding network of monasteries.

The Frankish church of the Merovingians was shaped by a number of internal and external forces: it had to come to terms with an established Gallo-Roman Christian hierarchy entrenched in a culturally resistant aristocracy; it had to Christianize pagan Frankish sensibilities and effectively suppress their expression; it had to provide a new theological basis for Merovingian forms of kingship, which were deeply rooted in pagan Germanic tradition; it had to accommodate Irish and Anglo-Saxon missionary activities on the one hand and papal requirements on the other. The Carolingian reformation of monastic life and teaching and church-state relations can be seen both as the culmination of the Frankish church and a transformation of it.