Count Reginar I of Hainault engaged in conflict with Zwentibold, the ruler of Lotharingia, in a significant confrontation near the location of present-day Susteren. The late 9th century was marked by the fragmentation of Carolingian power, which led to increased feudal rivalry among local lords. Reginar sought to expand his influence and secure his family's control over Hainault by challenging Zwentibold, who was perceived as a weak leader due to the weakening central authority of the Carolingian Empire.

The encounter took place against a backdrop of turbulent political landscapes, as Count Reginar capitalized on Zwentibold's vulnerabilities. The battle resulted in the death of Zwentibold, dramatically altering the balance of power in the region. This victory not only solidified Reginar's status among his peers but also revealed the persistent tensions between the noble houses of the time. Local allegiances shifted as new power dynamics emerged, reflecting broader trends in medieval Europe regarding political legitimacy and territorial control.

Additionally, the slain Zwentibold's death stirred further conflict among rival factions leading to a ripple effect in the politics of Lotharingia, demonstrating how individual battles could have long-lasting implications on regional governance. Reginar's actions also underscored the era's trend of noble warfare, which was often driven by personal ambition rather than broader national interests, paving the way for more localized feudal conflicts in the century to follow.