1The commune of Achenheim is located seven kilometres west of Strasbourg, in the Bas-Rhin department, on the southern edge of the Kochersberg plateau, at an altitude of 154 m, immediately north of the major Holocene bed of the Bruche River. The Strasse 2 site was excavated in 2016 by an Inrap team (Lefranc and Chenal 2018) and yielded 442 archaeological structures. The vast majority of these structures can be attributed to the Neolithic period, and consist of various segments and features of a continuous ditch enclosure, circular pits, extraction pits, a system of slot trenches, and a series of burials.

2The vast majority of the archaeological structures belong to the Bruebach-Oberbergen group (4400-4250 BC), including the ditch system, some extraction pits and at least 211 mainly circular pits (the total maximum number of these pits can be estimated at nearly 380 if we include pits that were not precisely dated). Four circular pits yielded burials (Lefranc et al. 2019). In terms of the number and density of the observed features and the presence of an enclosure with a continuous ditch, the Achenheim site appears today to be unprecedented in the Epiroessen of the Rhine plain. In order to account for the specificity of the site, it is vital to investigate its status and consider it in the regional context of the last third of the fifth millennium. Indeed, this context may have determined the advent of large ringed sites.

3The layout of the enclosure consists of a continuous V-shaped ditch, varying in width between 2.30 m and 1.36 m, with an average depth of 1.70 m, over a linear distance of 155 m. In the stripped area, the ditch is shaped like a segment of a circle interrupted by four openings. Two of these are materialised by simple interruptions in the ditch (openings A and C), while the other two are prominent constructions with different designs (openings B and D). Most of the course of the ditch shows a series of asymmetrical profiles, with a dip towards the outside of the enclosure. This observation, combined with the absence of ditched structures over a 3-to-5 m-wide strip behind the ditch, allows us to reconstruct - as was observed at the Berry-au-Bac La Croix Maigret site (Dubouloz et al. 1982)—an internal embankment with a slope of around 60%, extending over a height of around 6 m from the bottom of the ditch to the top of the embankment. This must no doubt have been accompanied by a palisade forming a parapet, in order to obtain a comparable system to the fortifications documented by ethnography in North America or New Zealand, for example (Best 1941, Jones 2004).

4The northern entrance can be compared to the “crab claw” entrance systems of the Peu-Richardian and Artenacian enclosures on the French Atlantic coast of France. At some well-preserved sites (Laporte 2009, Poisblaud 2014, Ard et al. 2018), these systems frame post-mounted structures. The latter can be identified with porches built to regulate access to sites assimilated to ringed habitats by recent research (Ard et al. 2018). These post structures, which protrude and interrupt ditches, are also documented in the Rhine area in the fifth and fourth millennia (Boelicke 1977, Boelicke 1983, Ratzel-Fabian 2000). It is likely that the ditches of the northern structure at Achenheim were built along the contours of an overhead structure. The shallow depth of the ditches in the structure could indicate that the embankment was removed to build a porch-like building on posts. The western prominence is only partially documented, and may have been a late addition. We do not know whether opening D was still used as a doorway during this possible second phase of development or whether it subsequently only opened onto a closed structure.

5Three sectors can be distinguished inside the enclosure: the area immediately behind the rampart, a silage area and a central area. A 20-30-metre-deep sector with large extraction pits can be outlined behind the ditch. The density of excavations is relatively low in this sector and it is possible, with reference to the example of Berry-au-Bac (Dubouloz et al. 1982), that this area close to the rampart was occupied by houses. Beyond this area, a sector with a high density of storage structures spread over a twenty-metre-wide ring, enclosing a space with very few traces of use. This could correspond either to a square or to the site of elevated structures. It should be noted that human remains, interpreted as the remains of a victory celebration, were deposited in this central space, pointing to the hypothesis of a community space.

6The lessons that can be drawn from the analysis of this enclosed settlement site are closely correlated with the importance of violence in society of the end of the fifth millennium in Lower Alsace. If we only consider the enclosure and the numerous storage structures, the village of Achenheim could be classified in the category of “central sites” (Petrasch 1990), a habitat and exchange centre as much as a ceremonial centre. The continuous enclosure could only have had an ostentatious function and probably indicated the special status of the village and its inhabitants. The presence of pottery imported from distant regions (Lower Bavaria, Franconia) reflects the existence of long-distance exchange networks and could support this view. However, the recognition of an enclosed settlement in a region where only low-density open settlements and “Rosheim-type” ceremonial enclosures were known until now (Lefranc et al. 2018), and the question of the context in which the construction of this barrier device was built must be addressed. In all cultural areas, the appearance of fortifications and the aggregation of populations in large complexes are indeed interpreted as markers of periods of conflict (Otterbein 1994, Keeley 1996), and appear to attest to assaults directed against entire communities in the context of inter-group conflicts rather than tensions between related groups engaged in feud-like conflicts (Solometo 2006). The appearance of fortified sites in a given region must therefore be considered as a strong indication of the presence of warfare. We have attempted to demonstrate elsewhere (Lefranc 2020) that this was indeed the case in Lower Alsace in the last third of the fifth millennium. The aggregation of a large population in a fortified settlement extending over at least four hectares coincides with an extremely violent historical episode, as evidenced by trophy taking and contempt for the enemy's corpse. These practices have been highlighted at Achenheim itself (Lefranc 2020), as well as at the contemporaneous site of Bergheim (Chenal et al. 2015). All the known ethno-historical examples show that these acts are part of high-intensity conflicts between groups considered to be foreign to each other and engaged in total wars (Harrison 2012, Boulestin 2020). We have known for a long time that the Bruebach-Oberbergen group, in the Middle Rhine Neolithic tradition, disappeared from Lower Alsace abruptly, giving way, without any transitional period, to the Western Bischheim, a group originating from the Paris Basin (Jeunesse et al. 2004). However, up until now, it was not possible to define the circumstances of this rupture. Today, the situation is different with the discovery of deposits indicating episodes of collective violence and the excavation of the fortified village of Achenheim. We can thus now, in accordance with the absolute chronology showing a rapid succession between Bruebach-Oberbergen and Western Bischheim between 4270-4210 cal BC (68%; Denaire et al. 2017), favour the hypothesis of an armed conflict between local groups and new arrivals, at the least, resembling a war of conquest. This hypothesis echoes many ethnological examples documented in non-state societies (Vayda 1976, Godelier 1996).

7Finally, it is important to emphasise the unique and contingent character of the episode identified here in the last third of the fifth millennium, i.e., regeneration through violence, which is opposed in all respects to the other regional sequences of cultural transition documented in Alsace. In fact, all of the latter are either part of progressive mutations or bear witness to processes of fusion and assimilation of groups with diverse origins (Lefranc 2020).

8In addition to the contribution of the site to ascertaining the historical processes at work in the last third of the fifth millennium, the relative abundance of exhumed material also provides us with the opportunity to better define the stylistic evolution of pottery, to characterise the lithic and bone tools, as well as the husbandry system of the Bruebach-Oberbergen group. The factorial correspondence analysis of a significantly increased regional ceramic corpus resulted in the subdivision of the Bruebach-Oberbergen into three stylistic stages. The first (BBOI) is marked by the generalization of spatula band decoration and vertical segments, which are specifically Bruebach-Oberbergen characteristics, in contexts still marked by a strong Bischheim-Rhine imprint. During the next stage (BBOII), the traditional Bischheim decorations gave way to covering orthogonal decorations often made with a comb. The last still poorly documented stage, characterised by the use of the four-tooth comb, is only present in the south of Alsace and appears to correspond to a late development of Bruebach-Oberbergen in a region not affected by the appearance of the western Bischheim.

9The Achenheim lithic series consists of 50 pieces, 16 of which are made of hard rock and 33 of siliceous rock, and is one of the most important collections discovered and studied to date for the Bruebach-Oberbergen group. The siliceous tools are mainly made on Cretaceous flint from the Paris Basin, and are part of the Middle Neolithic tradition. We observe continuity in tool types that appeared during the Grossgartach, around 4750 BC, with, in particular, composite sickle armatures, pointed blades and arrowheads characterised by increasingly invasive retouch. The tools on animal hard material (31 objects) are dominated by punches on metatarsals, fibulae and tibias and by bevels on large ruminant long bones or scapula. It is important to note that wild species (deer and fox) were widely used and represent 35% of the bone tool blanks. Finally, the faunal study shows a clear increase in pig breeding during the period. However, unlike other contemporaneous sites where this species represents the most important resource, cattle are predominant at the Achenheim site. This illustrates marked variability in the exploitation of resources from the domestic triad, which generally characterizes Bischheim and Bruebach-Oberbergen assemblages as a whole, and contrasts with the constancy of the composition of Grossgartach assemblages, where cattle are consistently predominant. This characteristic thus indicates a clear conversion of the supply system. It is also accompanied by evidence of the deposition of partial dog and pig, but also hare skeletons, or parts of skeletons, as at many other regional fifth millennium sites (Lefranc et al. 2019).