The Varangians as Rulers of Novgorod, c. 862
The Varangians, explorers, settlers, and conquerors from Scandinavia, fanned out across the eastern Baltic and Dnepr River regions in the 800s. According to legend, the Slavs of Novgorod expelled their Varangian conquerors, only to invite them to return as rulers when they could not rule themselves peacefully. Rurik became Prince of Novgorod, and the Varangian-Slavic mixture came to be called the Rus. Rurik's successors soon conquered nearby Slavic tribes as far south as Kiev, which became the capital of what is now commonly called Kievan Rus.
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The story of Novgorod's Slavs driving out their Varangians overlords only to invite them back when the Slavs realize they can't govern themselves is legendary but not necessarily true. It is also quite possible that the Varangians returned to rule Novgorod by force, intimidation, or guile but later popularized the story of being invited back to help legitimize their rule. If this is correct, then this may be the earliest known disinformation campaign in Rus/Russian lands, although by no means the last!
The story of the invitation of the Varangians comes from Tales of Bygone Years (also known as Chronicle of Nestor, or, in English, the Primary Chronicle). It was published in three editions in the early 12th Century and gives a history of Kievan Rus up to its time. It is believed one of its purposes was to emphasize the legitimacy of the Rurik dynasty in Rus lands.