Current scholarship tends to explain the silence of Greek sources with regard to Oleg's campaign by the inaccurate chronology of the Primary Chronicle. Some assume that the raid actually took place in 904, when the Byzantines were at war with Leo of Tripoli. A more plausible conjecture has been advanced by Boris Rybakov and Lev Gumilev: the account of the campaign in fact refers to the Rus'-Byzantine War (860), erroneously described in Slavonic sources as a Kievan failure.