What technologies did the Frank's use to defend themselves from the vikings?

The Franks employed several technologies to defend against Viking raids, including fortified castles and walls that provided strong defensive positions. They also utilized heavy cavalry, equipped with armor and lances, to counter Viking warriors effectively. Additionally, they developed better weaponry, such as crossbows and improved sWords, to enhance their combat effectiveness. The strategic use of local geography, including rivers and forests, also played a key role in their defense strategies.