The Varangian Guard was founded by Emperor Basil II in 988, with about 6,000 Swede and Rus-Viking warriors sent by Tsar Vladimir of Russia. Their name comes from an Old Norse word “var” which means “pledge.” The meaning is roughly “sharers of an oath.”
Varangian mercenaries had been serving in the Byzantine army and navy as early as 902, but Basil II formed them into a distinct regiment to act as his Imperial bodyguard to thwart shifting loyalties of the native Byzantine guardsmen. The guards' loyalties were sworn to the position of Emperor, not the individual that sat on the throne. They were known as the axe-bearing guard, from the enormous two-handed axes they carried. They served at the forefront of many of the Empire's battles, fighting Turks, Bulgars, Crusaders, Normans, and many others, used in battle only during critical moments or where the battle was most fierce.
The Varangian Guard was the best paid of all the Emperor's troops. It became common for Norsemen to go to south through what is now Russia and the Ukraine to Byzantium from all over Scandinavia, spend time in the Varangian Guard, and return home quite wealthy. The Guard was disbanded after Constantinople’s capture in 1204.