Keep pulling the thread on Lars Brownworth.
The Byzantine emperor Basil II formed the Varangian Guard in the late 900s, an elite bodyguard unit composed of Vikings.
Knut the Great, a Danish ruler, created the North Sea Empire in the early 11th century, uniting England, Denmark, and Norway.
In June 793 AD, Vikings likely originating from Norway conducted a raid on the monastic community on the Holy Island of Lindisfarne, where they killed the inhabitants and plundered the site.
The Viking leader Ragnar Lothbrok sacked Paris in 845 AD, an event which prompted subsequent waves of large-scale Viking invasions throughout the 860s.
The Great Heathen Army, a large coalition of Viking forces led by the sons of Ragnar Lothbrok, invaded and eventually conquered England starting in 865 AD.
In 911 AD, the Viking leader Rollo and the Frankish king Charles the Simple signed the Treaty of St. Clair-sur-Epte, which granted Rollo land that would become Normandy in exchange for defending the coast against other Vikings.
The Normans, descendants of Viking settlers in France, conquered kingdoms at both ends of Europe, including Sicily and England, and founded two of the four most powerful states in medieval Europe.
The Byzantine Empire served as a crucial buffer state, protecting a developing Europe for centuries from threats coming from the east.
Swedish Vikings, known as Varangians, established the state of Kievan Rus after taking control of Novgorod and Kiev in the 9th century.
The collapse of the Byzantine Empire began after the death of Basil II in 1025, leading to the disastrous Battle of Manzikert in 1071 where the Seljuk Turks destroyed the Roman army and overran Anatolia.
Greek fire, a Byzantine weapon, was a form of napalm likely made from naphtha and oil that would ignite on contact with oxygen and continue to burn on water.
The Byzantine Empire used Greek fire to defeat a Viking fleet attacking Constantinople in 944 AD by setting the sea on fire.