Varangians first appear in the Byzantine world in 839, when the emperor Theophilus negotiated with them to provide a
few mercenaries for his army. Although the Rus' often had peaceful trading relations with the Byzantines, Varangian
raiders sometimes attacked from the north. Such attacks came in 860, 907, 911, 941, 945, 971, and finally 1043. These raids were successful only in causing the Byzantines to re-arrange their trade treaties; militarily, they were always defeated by the superior Byzantines, especially by the use of Greek fire.
The ruling class of the two powerful city-states of Novgorod and Kyiv eventually became Varangian, and the Byzantines soon acquired an official mercenary force that became the Varangian Guard. This occurred in 988, when Kyivan Prince Vladimir the Great converted to Orthodox Christianity. In exchange for a marriage to Basil II's sister Anna, Vladimir
gave Basil 6,000 Varangians to use as his own personal bodyguard. The Varangian Guard was one of the fiercest and most loyal elements of the Byzantine army, as described in Anna Comnena's chronicle of the reign of her father Alexius I, the Alexiad. Their main weapon was a long axe, although they could also be skilled swordsmen and archers.
They were the only element of the army to successfully defend part of Constantinople during the Fourth Crusade,
although the Guard was apparently disbanded after the city's capture in 1204. By this time, the term Varangian
referred to any mercenary from northern Europe, and the Guard was probably composed more of English, Scottish and
Norman mercenaries than Russians or Scandinavians.