A new study from the University of Cambridge has revealed that severe and consecutive droughts in the late 4th century played a pivotal role in the 'Barbarian Conspiracy' of 367 CE, a critical event in the history of Roman Britain. The researchers used oak tree-ring data to reconstruct the climate conditions of southern Britain during and after the invasion, providing valuable insights into how environmental factors can shape historical outcomes. The Barbarian Conspiracy of 367 CE The 'Barbarian Conspiracy' was a coordinated invasion by the Picts, Scotti, and Saxons that posed one of the most significant threats to Roman control of Britain since the Boudiccan revolt in 60-61 CE. According to contemporary Roman accounts, the invasion was marked by several destabilizing events. The garrison on Hadrian's Wall rebelled, allowing the Picts to attack from the north, while the Scotti and Saxons invaded from the west and south, respectively. These incursions resulted in widespread chaos, with small bands of invaders roaming and plundering the countryside. Senior Roman commanders were captured or killed, and some soldiers even deserted to join the invaders. Climate and Impact The study, published in the journal Climatic Change, links the invasion to extreme drought conditions in southern Britain from 364 to 366 CE. By analyzing tree-ring records, the researchers reconstructed the temperature and precipitation levels of the region during this period. They found that average monthly rainfall in the main growing season (April-July) was 51 mm from 350 to 500 CE. However, during the drought years, rainfall plummeted to 29 mm in 364 CE, 28 mm in 365 CE, and 37 mm in 366 CE. These conditions were unprecedented in the historical record of the region, and no other comparable droughts were identified in that 150-year span. The agricultural landscape of Roman Britain was heavily reliant on spring-sown crops like spelt wheat and six-row barley, which are susceptible to early summer droughts. The prolonged drought from 364 to 366 CE would have severely impacted crop yields, leading to significant food shortages. Roman chroniclers, such as Ammianus Marcellinus, noted that by 367 CE, Britain was experiencing extreme famine. Societal Breakdown and Military Weakness The food shortages and subsequent famine had far-reaching consequences. The drought-induced agricultural crisis would have undermined the Roman military's ability to maintain order and loyalty among its troops. The reduced grain supply to Hadrian's Wall, a critical military frontier, likely contributed to the garrison's rebellion, allowing the Picts to breach Roman defenses. Similarly, the researchers suggest that the lack of food and resources may have led to additional desertions among Roman soldiers, further weakening the province's defenses. The geographic isolation of Roman Britain, coupled with the severity of the drought, hindered Rome's ability to send immediate relief. During this period, Roman resources were already strained due to the need to support the Rhine frontier and increased migratory pressures. This combination of factors limited the resilience of the local population and the military, making the province particularly vulnerable to external invasion. Broader Implications The researchers extended their analysis to the entire Roman Empire during the period from 350 to 476 CE, reconstructing climate conditions in the years leading up to 106 battles. They found a statistically significant correlation between dry years and the incidence of battles, suggesting that climate-induced food shortages and societal destabilization were common precursors to conflict throughout the empire. Industry Insights and Evaluations The study's findings highlight the intricate relationship between climate and human conflict, a topic that is increasingly relevant in the modern context. As Tatiana Bebchuk, a co-author from the Department of Geography at the University of Cambridge, noted, extreme climate conditions often lead to hunger and societal challenges, which can culminate in outright conflict. This research provides a historical parallel to contemporary concerns about climate change and its potential to exacerbate social and political tensions. The University of Cambridge, known for its cutting-edge research in geography and environmental science, has a strong track record in climate studies. The study's lead researcher, Charles Norman, was supported by a John Hughes PhD Studentship from Wolfson College, while Professor Ulf Büntgen received funding from the Czech Science Foundation, the ERC Advanced Grant, and the ERC Synergy Grant. The collaboration with the Generaldirektion Kulturelles Erbe Rheinland-Pfalz in Trier further underscores the interdisciplinary nature of this research, which combines historical accounts with climatological data to provide a comprehensive understanding of the events leading up to the 'Barbarian Conspiracy'.