BTW, does the book mention that many White Rusians came to fight against the Communists durng the Spanish Civil War?
I don't believe it mentions that. What the author is doing in not so much describing a linear historical or political history, but outlining the underpinnings of Great Russian culture; starting in Kiev, following the move north and then the rise of Muscovy, the Russian Empire and lastly the Soviet Empire (it was written in the 60's). One of the main themes is the history of interaction with the many sided entity that was and is the "West". He describes how western ideas were absorbed and feared, and ironically how western ideas were used in opposition to the incursion of other western ideas; and also how opposition to the west was a convenient steamvalve for Muscovy for dealing with political dissent, and ultimately how opposition to the west was really often just projected self criticism (he notes this about Roman Catholicism in particular). He describes what would probably be called a love/hate relationship, and shows how Dostoevsky both admired and rejected the west for instance; on the one hand lauding Cervantes and on the other his depiction of Seville. He also notes how two of the sides that were most intractable in their positions regarding the reunion Council of Florence were the Spanish and the Russians.
The book I guess you could say is thematic, and by trying to show the underpinnings of the culture, you can look at various historical points to see how there is a clear line of progression and consistency. One point the author makes is the fear of cosmopolitanism, and the poignant destruction of west facing Novgorod by Ivan IV and the fear and suspicion of those who were too much in contact with the West. The author makes a parallel to the Russians who returned from fighting in the International Brigades in the Spanish Civil War, and notes that participation in the Republican cause was essentially an automatic ticket for being a victim of the Stalinist purges.