How did Louis I respond to Viking raids and threats in northern Europe?

To address the threat posed by Vikings raiding the coasts of the North Sea and the Atlantic Ocean, Louis I (the Pious) attempted a diplomatic and religious approach rather than relying solely on military force. He proposed to evangelize the Scandinavian world in the hope of averting further aggression.12

This mission was entrusted to St. Ansgar, but it ultimately proved to be a failure. While Louis sought to mitigate the danger through these efforts, the Viking raids continued to escalate in magnitude and frequency during his reign, particularly targeting churches and monasteries for their wealth. Other defensive measures, such as fortifying towns or employing counterattacks, were utilized in the broader Frankish territories to combat these incursions, though these were often local initiatives rather than a centralized imperial policy under Louis I.123