The raid of Paris in 845 was a devastating attack on the Frankish city by Danish and Swedish forces. While the city itself was not taken by the hostile forces, it resulted in massive amounts of destruction in Paris, not to mention the theft of gold and the kidnapping of civilians. It is generally seen as the cause of the First Viking War, which lasted until 864.
Attacks by the Vikings had occurred before in the Frankish Empire. An attack in 799 led to Charlemagne's creation of a naval defense grid around Francia. The defenses held numerous times, including during attacks throughout the 820s and 830s. Unfortunately, however, this grid was unable to prevent large numbers of ships from entering Frankish waters. Furthermore, the Frankish navy had been largely neglected for some time prior to 845.
While hostilities between Francia and the Vikings were present before the raid, war was never officially declared until after the Raid of Paris. Systemic attacks along the English Channel broke through Francia's navy before attacks on more cities around Francia continued. The attacks were few and far in-between, however, as the Vikings knew of Francia's power. However, the promise of riches outweighed the fear of a massive war with the Franks.
Invasion of the Seine
In 845, a Viking warlord known as Reginherus invaded the Seine River with a force of 120 ships. Reginherus, popularly known as Ragnar Lodbrok, had been responsible for numerous other raids around Europe, especially in the Kingdom of Northumbria. The Franks learned of their invasion and attempted to ambush the forces along the Seine river. The armies were placed on either side of the river. One of the divisions was attacked and hanged by the Vikings. Their deaths were sacrifices to the Norse god Odin and the brutality of the murders inspired fear in the Frankish forces that were left.
Paris itself was invaded on either Easter Sunday or Easter Day, a Christian holy day. During the siege, a bout of plague broke out in the Viking camps. Apparently, the forces acted upon the words of a Christian prisoner who advised them to fast. While the fasting was advised for religious reasons, the fasting allowed the plague to subside. With the Vikings strong again, they were able to again attack Paris. The city, confined to an island at the time, was unable to defend itself against the Vikings and was quickly occupied.
The Vikings occupied Paris for an unspecified amount of time. They refused to leave unless a ransom of 7000 livres was paid to Ragnar's forces. While the Franks initially refused to pay, Lothair I paid the ransom. With the ransom paid, the Vikings left Paris and went back up the Seine river to their homelands, taking goods and captives with them.
The Raid of Paris is remembered as the cause of the First Viking War, a war of revenge on the Vikings that had been terrorizing the area for some time. The short-term effects of the raid led to a damaged Paris and an embarrassed Francia. Lothair is still poorly remembered for giving in to the demands of the Vikings. Nevertheless, Paris eventually rebuilt and the Franks regained their honor in the later stages of the First Viking War.