The idea that the Carolingian mayor of the palace and future king Pippin I transformed the putative institution of the field of Mars into a field of May has exercised scholars for more than three centuries. Based on the comments of a small number of authors, including Gregory of Tours, Fredegar, and Archbishop Hincmar of Reims, many historians have developed elaborate theories about the existence of a specific field or location on which the Merovingian and/or Carolingian rulers mustered their armies, the continuity of the importance of the erstwhile Roman god Mars in the early Middle Ages, and the supposed transformation of the organization of the armies of the Franks under Charles Martel. In this new intervention into the age old problem of the Frankish field of Mars, Alain Stoclet, associate fellow at the Centre for Medieval Studies at the University of Toronto, seeks to address two main questions: what was the field of Mars in the 8^th century, and why did Pippin III/I change the field of Mars to a field of May?

The volume is divided into two main parts. The first half of the text is organized in six chapters, while the second half of the text is divided into eleven appendices. Following an introduction and prologue in which Stoclet sets out his goals for the study and gives an overview of the source material, he begins in chapter one with a detailed examination of the influence that Charles du Fresne, the lord of du Cange, exercised on earlier historians investigating the meaning of the term campus martius. He then turns to a discussion of the question of whether the actual field of Mars at Rome had imitators in the provinces and concludes that most of the references to such fields come from the 11^th century and later. Stoclet grants that some later Roman authors, such as Ammianus Marcellinus, noted the presence of a field of Mars at cities such as Paris.

But he asserts that in the absence of evidence for the maintenance of such mustering and training sites, there is no reason to believe that there were literal fields of Mars anywhere in the Regnum Francorum under the Merovingians or Carolingians. In the final section of the chapter Stoclet turns to the scholarly traditions associated with Heinrich Ludolf Ahrens, Heinrich Brunner, and Michael Sierck regarding the nature of the campus martius, and its supposed transition, and rejects them all as inadequate. Strikingly, however, Stoclet does not address the findings here of Bernard S. Bachrach, a point to which I will return below.

In the second chapter Stoclet investigates the appearance of the term »field of Mars«, in its various Latin forms, in later Roman sources up to the reign of Charlemagne, with a particular focus on ceremonies involving the naming or investing of an emperor. He emphasizes in this context the Carolingian effort to defame their Merovingian predecessors with a focus on the importance of Einhard’s discussion of the ox cart in which the last of the Merovingians are reported to have traveled to a major Frankish assembly. As is well-known to most early medievalists, the ox cart was used by later Roman officials in formal processions, which demonstrates an important element of ceremonial continuity under the Merovingians.

Stoclet turns his attention in chapter three to juridical texts, including both charters and law codes, to identify when the Franks held assemblies under both the Merovingians and Carolingians. He then turns to an examination of the holding of assemblies by the Lombards and Alemanni. Stoclet observes that the month of March saw the most assemblies under the Merovingians as well as under the Carolingians. However, whereas March represented an overwhelming mode, in statistical terms, for the holding of assemblies under the Merovingians, the Carolingians held almost as many assemblies in June and July as they did in March, and also held notable numbers of assemblies in both May and August. Based on the dating of charters, Stoclet also observes that assemblies under the Merovingians and Carolingians often lasted many days or even weeks and were not limited to the first day of March as some scholars had argued. In turning to the legal sources and charters for the Lombards and Alemanni, Stoclet observes a similar pattern in which March assemblies were the most frequent. He argues, however, that it would be incorrect to assume that the inspiration for such March assemblies came from the Franks.

In chapter four Stoclet moves from juridical to narrative sources and identifies two major groups of texts that use the term campus martius or similar terminology in the Carolingian period. The first of these groups of texts refers to the campaigns by King Pippin I in Aquitaine in the 760s and the second to the campaigns by Charlemagne against the Saxons in the 770s. After analyzing each of the texts in both groups with respect to the inspirations and motivations of the authors, and their various dates of composition, Stoclet draws three major conclusions: 1. the Carolingians experimented with the date of their general assemblies, 2. the narrative sources have an overwhelmingly Austrasian bias, 3. the use of the term campus martius to describe the mustering of Charlemagne’s armies for campaigns against the Saxons was based on the knowledge by the authors of these texts that this term was used to denote the mustering of armies by Pippin I.

Stoclet continues his discussion of narrative sources in chapter five, with a focus on those texts that considered the concept of the campus martius under the later Merovingians. He returns to the idea that the Carolingian sources were marked by a strong tendency to defame the Merovingians in an attempt to justify the usurpation of the royal authority by Pippin I. Stoclet also examines a number of Roman works, such as the first century B. C. treatment of military matters by Cincius, which survived in fragments into the Carolingian period, as well as various Roman laws detailing the legitimate use of violence. Taken together, Stoclet intends this discussion to highlight the military nature of the campus martius.

The sixth chapter begins by returning to the question of why Pippin supposedly substituted a field of May for the field of Mars. Stoclet discusses in considerable detail the argument by Sierck, mentioned above, who claimed that Pippin sought to avoid mustering troops during Lent by moving back the field of Mars to May. In this context, Stoclet examines the sources that treat the forced abdication of Emperor Louis the Pious in 833 and the trial in which one of the charges against the ruler was that he mobilized an army to invade Brittany during Lent. However, Stoclet disposes of this argument by pointing out that Carolingian rulers mobilized armies at all times of the year, including during Lent.

In his brief conclusion, Stoclet returns to the two questions motivating his study, arguing first that the field of Mars or the field of May was not a specific place. He also observes that assemblies involved several different elements: judicial, political, and military. Ultimately, he argues, based in large part on his findings in chapter four, that the supposed end of the campus martius and the field of May, or at least the use of this terminology, was due to the division of the Frankish empire into regna during the 780s, and to the need to develop a new ceremonial to account for the lack of a unitary Frankish government. The remainder of the volume consists of 200 pages of appendices, which demonstrate Stoclet’s considerable erudition with regard to numerous topics such as the manuscript traditions of the texts that attest a campus martius, and a detailed treatment of the Carolingian assembly at Paderborn in 785. For the most part, these appendices are tangential to the main investigation in the book and serve to highlight ancillary points addressed in passing in the text.

Overall, Stoclet offers a prodigious scholarly contribution that addresses a vast array of questions and will be of considerable use to many scholars, particularly with respect to the histories of the various sources that he discusses. However, as a monographic study of the campus martius this work is unsuccessful. First, Stoclet does not address, much less refute, the basic modern study on the campus martius by B. S. Bachrach¹, which demonstrated that the very idea that Pippin changed a field of Mars to a field of May is a historiographical myth based on the efforts of scholars to use for their own purposes the play on words by Gregory of Tours, Fredegar, and Hincmar of Reims.

In short, Stoclet’s entire discussion of the field of Mars is based on the false premise that Pippin actually changed anything with regard to the holding of assemblies, and particularly the mustering of the Frankish army for campaign. Secondly, Stoclet does not address, reconcile, or even cite, the study by B. S. Bachrach regarding the two-fold assembly system utilized by Charlemagne for military campaigns, which was treated in detail by Charlemagne’s cousin Adalhard of Corbie in »De Ordine Palatii«.

In short, Charlemagne summoned military advisors to the winter court to plan for the year’s military operations. This first assembly drew up capitula laying out the plans for the campaign and set in motion the subsequent assembly of the army, which took place once weather conditions made military operations possible. These general musters of the Frankish army happened at all times of the year, and often in two or even three places in the same year, as the Carolingians mobilized several armies to attack their enemies in a pincer movement. Bachrach’s observations on these points, which are based on a close analysis of military matters, will help readers navigate the complex treatment of other questions by Stoclet.