 
 <prompt> Wetin start for Dnieper? Based on di last question, write one context wey contain di answer. E fit be 1 - 20 sentences. Context: <response>: Relations between the Rus' and Byzantines don dey get more complex afta Oleg take control over Kiev, wey dey show commercial, cultural, and military concerns. The wealth and income of the Rus' dey heavily depend on trade with Byzantium. Constantine Porphyrogenitus describe how the princes of Kiev dey take tribute from client tribes, gather dem into plenty boats, carry dem down the Dnieper go Black Sea, and sail go the estuary of the Dniester, the Danube delta, and then go Constantinople. Dem dey carry silk fabrics, spices, wine, and fruit come back. The importance of this trade relationship dey lead to military action when wahala show face. The Primary Chronicle talk say the Rus' attack Constantinople again for 907, most likely to secure trade access. The Chronicle dey praise the military strength and smartness of Oleg, with plenty legendary details. Byzantine sources no mention the attack, but two treaties for 907 and 911 outline trade agreement with the Rus', the terms show say the Byzantines dey under pressure, wey make dem give the Rus' space and supplies for their traders and tax-free trading rights for Constantinople. 