Every time I try to read up on the Merovingians and understand the early Middle Ages, something like this (from Wikipedia) happens:
During the final century of Merovingian rule, the kings were increasingly pushed into a ceremonial role. Actual power was increasingly in the hands of the mayor of the palace, the highest-ranking official under the king.
Clotaire's son Dagobert I (died 639), who sent troops to Spain and pagan Slavic territories in the east, is commonly seen as the last powerful Merovingian King. Later kings are known as rois fainéants ("do-nothing kings"), despite the fact that only the last two kings did nothing. The kings, even strong-willed men like Dagobert II and Chilperic II, were not the main agents of political conflicts, leaving this role to their mayors of the palace, who increasingly substituted their own interest for their king's.
Two paragraphs, completely (and seemingly, to me) brushing over what must have been some major power shifts in the Merovingian kingdom, without any explanation how it happened, whether the Merovingian monarchs retained any level of power, whether there were any struggles or efforts to regain their power, what role the monarchs had in Merovingian society, how they were seen abroad, what factions there were, whether the kings were content with their diminished role, what specifically made the mayors so strong, etc.
And it's not just Wikipedia. Everywhere I look, it seems that the transition from the Merovingian kings to the Frankish empire(s) starting with Karl Martel is incredibly blurry, getting glossed over in a half-sentence in the passive voice.
So, what's the straight dope on the Merovingians? What happened to push what was arguably a formidable dynasty, to the sidelines? Is it just a matter of "we don't really know, either"? Or is there somewhere something to read that has a bit more meat to it, as it were?
So I'm pretty sure that Wickham touched on this phenomenon in his Inheritance of Rome book. I just looked it up, p.117-120 for the right pages, with p.576 for the accompanying notes for other readings. However, this book is from 2009, which means its probably a dozen or so years behind whatever current scholarship is out there.
Wickham doesn't offer a concrete answer as to why, presumably because the scholarship is so hotly debated that I imagine only speculative answers would suffice. His best guess is that we're dealing with a devolution (always present in any state) of power away from the center and towards the regions, a centrality that could only be reinforced by war (e.g. Charles Martel's conquest of the south), and with more functional military power being held by the Mayors of the Palace, the Kings were being relegated to ceremonial roles.
If you want the primary sources, you probably want the Chronicle of Fredegar and its continuation, which covers that period as a relatively succinct narrative history with a pro-Carolingian bent. Otherwise, you will have to cobble together everything from the assorted hagiographies that were produced at the time. I know Fouracre edited a source book on Late Merovingian France for sources that aren't Fredegar if you want more detailed primary sources.
To me, this is not a uniquely Merovingian phenomenon. You see the tale replicated all over the place, from the Japanese Shogunate, to the Abbasid Caliphate, to even Late Roman and Chinese child emperors. This says to me what we're looking at is a human political power phenomenon. You have a shift in the center of power from the "capital" to the regions, from the combined de iure/facto leader to the de facto only. Why does this happen? Who knows, especially if we're not trying to be teleological or determinist.
My best hot take on it, as a non-specialist, is that the Merovingian political system was always highly fragmented, with its multi-king system, meaning there was a high degree of pre-existing regionality to the kingdom. As mentioned, centralization had to be done by force, and required justification and collaboration with the aristocracy. A long period without royal civil war after Clotaire II meant that competition moved down to the non-royal mayoral level. Sorta like when you're playing Crusader Kings as a king, and all your counts and dukes are at war with each other, but they respect you as king. Nominally you're in charge, but the functional skill set of warfare and accompanying resources brought on by successful contests are accumulating under these subleaders, rather than you. And at a certain point, you get a tipping point. And now you're only left with some rois fainéants (weak kings).
But, this is only my hot take. Plenty of others exist, and the lack of a single narrative (probably a good thing) means academics in pay grades above me can't agree either.
It is true that OP's question is not so easy to offer a definitive answer mainly due to the dearth of reliable contemporary sources from later Merovingian kingdom of the Franks.
At least, however, we know the main source of this histriographical (in both senses) tradition of regarding late Merovingian ruler as rois fainéants. It's a retrospective view provided by Carolingian historical writings, such as Einhard (around 830) probably summarizes in the following well-known passages:
'......Although it might appear that the family came to its end in him [Childeric II], actually it had possessed no vitality for a longtime already and could boast nothing better for itself than the empty title of the king. Indeed, the resources and power of the realm were in hands of prefects of the palace, who were called mayors of the palace and to whom the highest authority belonged. In fact, nothing was left to the king except to be happy with the royal title and to sit on his throne with his flowing hair and long beard and to behave as if he had authority......(Einhard, The Life of Charles the Emperor, Chap. 1, in: Noble ed. 2009: 24).
This is primarily the retrospective comment narrated by the usurper/ victor of the power struggle in the 8th century, and at least some new studies in the 21th century also focus on another, much less known aspect of the royal authority of Merovingian rulers during the late 7th and early 8th centuries. To give an example, Le Jan points out that three late Merovingian rulers, namely Clovis IV (r. ca. 690-95), Childebert III (r. 694/5-711), and Dagobert III (r. 711-15) issued a great number of royal documents (mainly the judicial records), and in one famous judicial case in 710, King Childebert III could still favor St. Denis (monastery) over Mayor Grimoald of Neustria (sub-kingdom) who was a son of Pippin of Heristal, the Pippinids.
Some undeniable changes indeed occurred in late 7th century, however:
Then, how did this power shift among the sub-kingdoms of the Merovingian Franks happen?
One possible answer, often suggested by the newer studies, is the rising socio-economic importance of the North Sea commerce and its associate river traffics in Rhein-Maas area. The mouth of these rivers also had the petty kingdom of the Frisians who connected Gallia with Great Britan as well as Scandinavia by way of ship traffics in the North Sea (the Franks also increasingly expanded their influence over the Frisians from ca. 700 onward). The political eminence of the Carolingians from Charles Martel, in a sense, could be fruits of the North Sea as well as river traffic and commerce (Note that Charles Martel himself had probably been an illegitimate son between Peppin of Heristal and Alpaida, a daughter of the local magnates from now Maastricht, the downstream regions of rivers pouring into the North Sea).
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Merovingian Francia already went through a serious crisis by the late VIth and early VIIth centuries in what had been dubbed the 'royal faida' between the successors of Chlotar I (dominated by the powerful figures of the queens Brunhild and Fredegund.) that is a logic of paralegal vendetta practised between non-state actors and usually regulated by the king there elevated to the state affairs and without paramount power to curb it down. This "Fifty Years' War" wasn't a continuous military conflict, but had nothing to envy to other protracted wars in History as the Hundred Years War or the Thirty Years War when it come to intrigues, assassinations, backhanded negotiations, foreign intervention, etc. accompanied by a great involvement of Francia's military and administrative aristocracies (which tended to blend) and bishoprics eventually culminated with Chlotar II victory but brang decisive changes in the realm.
First, while the division of the Frankish realm into several courts didn't implied its political balkanisation generational habitude and regional conflicts led to the notion of a regionalized, decentralized royal power. As he became the monarchus of Francia, Chlotar II nevertheless had to preserve the continuity of an Austrasian and Burgundian court even while he didn't held one there, cementing the tripartition of his realm into the three core sub-kingdoms of Neustria, Austrasia and Burgondia (Aquitania being a perpetually aborted fourth part), that regional aristocracy came to identify itself with. Majordomos (majors of the house/palace) thus became a more important function that they were, managing these courts and becoming an intermediary between regional aristocracies and the king. Still, having a royal court also meant that the regional aristocracy wanted to have a kind “at disposal” if possible : hence why Chlotar II made his sons king in Austrasia and Dagobert doing the same in Austrasia (decidedly with a strong identity) while they were still alive (when this sort or partition was more usually done as succession).
Then, part of this aristocracy had changed; not that the Frankish public servants disappeared as a social corps (far from it, the late VIth century saw an increase of administrative functions and noble titles), but some families seem to have disappeared or met with significant losses eventually replaced by minor or other branches without the same tradition of public service than held so far by the old Roman elites. Instead we get the impression of a more warlike nobility, whose distinction with the Frankish elite (itself essentially romanized) is hard to pinpoint, and more driven by familial and individual self-interest than by a sense of public service whereas bishops inherited the old senatorial and equital culture of service becoming more and more present in administration and in local management and while still nominated by the court, benefiting from a legitimacy of their own relatively to lay nobility.
Eventually, although both Guntramm and Childeric II campaigned respectively in Septimania and Italy, not only the time of the great conquests were over but due to the ongoing civil war, peripheral peoples more or less submitted or within the sphere of influence to reclaim a greater autonomy (as the Varini, crushed by Childeric II, Saxons shaking free from Frankish tribute, Bretons raiding and conquering more of modern Brittany, Gascons appearing all over southern Aquitaine, etc.)
Both of Chlotar II and Dagobert I's reigns were energetic and dynamic enough to overcome the challenges of the early VIIth century doubled by a marked decline of the Mediterranean connections, but while their rule wasn't overly challenged as while they kept the upper hand on nominating, awarding or destituting public servants; they had to take in account a growing regionalisation in recruiting and missioning them (even if it wasn't systematic especially for prestigious functions), greater hunger for functions (and the benefits it could give either fiscal/landed revenues form the royal treasury), greater use of normally regalian prerogatives, etc. both of these kings regularly intervening and edicting on proper state service and fiscal management. Note that is likely wasn't the result of a negotiation between the kings and the aristocracy at large, but the the kings taking in account the situation at their benefit or the state's (Merovingians already tended to cut corners whenever they could to make it work), and the Eastern Roman Empire enacted similar decisions in Italy after its conquest which had been argued having served as a model for Merovingians. Having still the power to award (even if extremely rarely, up to life or entry in religious life) and to dismiss public servants and majordomos was, eventually, both a display and a means of their political supremacy, they otherwise were aware that the aristocracy didn’t blindly accept an entire royal control of these state mechanism.
Success of these kings in dealing with their periphery was more...mitigated : Chlotar and Dagobert managed to force Saxons into tribute, but met with much more hardships against Vascones, Bretons, Samo's Slavs (who even managed to defeat the royal army, thus weakening royal prestige and authority in Frankish Germania). If such defeats weren’t unheard of and while humiliating, could be recovered from by later expeditions, the incapacity of later Merovingians to effectively deal with these problems would be a source of loss of prestige, military capacities and temptation for the Frankish aristocracy as a whole.
For the first half of the VIIth century, then, the situation could be seen as a net improvement from the previous civil war, even at the cost of giving the aristocracy more leeway. Unfortunately, the situation quickly turned more grim for the dynasty.
The immediate reason is to be found in the ‘royal turnover” that marked the rest of the VIIth century : Sigebert and Clovis, Dagobert’s sons, were barely able to rule long enough under the tutelage of their mothers, great aristocrats and majordomos to produce heirs and die in their mid-twenties. These rege,coes weren’t necessarily a period of turmoil, and arguably could be seen as a moment of dust settling, temporisation, backhanded agreements, from which the majordomos benefited greatly not yet as ruler-de-facto but irreplaceable intermediaries between the nobility and their king in a given sub-kingdom. And while Dagobert had been able to shackle off the tutelage of Peppin I himself, by picking his own men, his successors didn’t have the capacity doing so due to the short time they had building up their own networks : it was up to the regional aristocracy to choose or support candidates to this post, someone they’d be both familiar with and acknowledge his authority over them partly born of a semblance of cursus honorum in royal administration, partly out of their own familial network. Their power, while outside the traditional agreements on Frankish public (but, then again, these were a permanent institutional tinkering from the palace), was accepted and complementary of royal authority : keeping close to the kings, the queen mother, trying to make works one self-interests with a sense of duty, etc.
As such, the majordomos of the two kings were taken (through a mix of nomination and election by nobility) from both familiars of the dynasty but also powerful men in the region able to make themselves (and thus the king) obeyed fully : Erchinoald in Neustria, related to Merovingians; and Grimoald in Austrasia after he saved Sigebert who thanked him killing the previous majordomo and giving Grimoald its charge. A good part of the activity of these men were to preserve this familiarity and not be chased off their prestigious charge as Peppin of Landen (Grimoald’s father) had been by Dagobert : Erchinoald by giving Clovis II an enslaved woman as a wife, Grimoald by adopting Sigebert’s son (and probably not the contrary). Meanwhile, in order to keep their own agency, they endorsed what were so far regalian display as a domineering figure above regional aristocracy whose a large part were his relatives, clients or opponents : most notably the practice funding and supporting religious establishments but more generally having a strong influence on royal decisions, establishments, nominations, etc. becoming something mi-flesh, mi-fish in between the paramount aristocrat and the paramount administrator.
The royal prestige and authority, as much as some restraint in advancing one’s interest besides moments of crisis and social insecurity (the irrevocability of functions proposed by the majordomo of Burgundy being largely ignored) was enough to not let the situation going awry, but some practices ill-considered before and still so even in the mid-VIIth century were considered more acceptable : profiting from taxes and fines instead of giving them to royal treasury, prolongation of offices during years or decades, growing confusion between charges and sources of power (bishops going to war, counts dealing with religious business, peripheral dukes transmitting their power) etc. Something was rotten in the kingdom, and as, both kings died young, leaving the realm going through yet other royal minority, on which the energetic policies or even Machiavellian decisions of former Merovingians (not hesitating to kill or remove a nephew or a cousin to hold their part of the realm) was replaced of those of the majordomos.
This question and the resulting answers demonstrate, for me, the Epitome of Why I Love This Sub!
A curious mind takes the time to ask a question; generous souls with the knowledge to do so, take the time to answer thoroughly, list resources, and respond to comments.
Well done, all!
Thank you, mods for keeping the standards high, we all profit from your efforts!